Common Vietnam SIM Card Problems & How to Fix Them

Vietnam‘s SIM card rules tightened again in 2025, and by 2026 the government is running near-zero tolerance on improperly registered SIMs. Travelers who buy a SIM from a street vendor, skip the passport photo step, or use a card registered to someone else are finding their service cut without warning — sometimes on day two of a two-week trip. This guide covers every common SIM problem you are likely to hit in Vietnam in 2026, with specific fixes, USSD codes, APN settings, and carrier app names so you can solve issues yourself instead of hunting for a carrier store in the rain.

Vietnam’s Three Major Carriers — Who They Are and Which to Choose

Three carriers dominate the market. Smaller operators like Vietnamobile and Gmobile exist but their tourist packages and coverage are thin enough that most travelers should ignore them.

• Viettel — The largest carrier in the country. Strongest signal in rural areas, mountain passes, and places like Ha Giang or the Central Highlands. If your itinerary goes beyond major cities, Viettel is the safest choice. Official website: vietteltelecom.vn
• Mobifone — Excellent in urban centers and popular tourist corridors (Hanoi, Ho Chi Minh City, Hoi An, Da Nang). Competitive pricing and a solid app. Official website: mobifone.vn
• Vinaphone — Government-owned, reliable in cities, pricing is often the most affordable. Good fallback option. Official website: vinaphone.vn

For most visitors doing a north-to-south or coastal route, Mobifone works fine. For anyone heading into remote areas, pay the slight price premium for Viettel.

Your SIM Options in 2026 — Physical SIM vs eSIM, Where to Buy

You have two realistic options: a prepaid physical SIM or an eSIM profile downloaded before or after landing.

Physical Prepaid SIM

Kiosks sit immediately past customs at Noi Bai (Hanoi), Tan Son Nhat (Ho Chi Minh City), and Da Nang International Airport. Wait times run 5 to 15 minutes per customer during busy arrival windows — that familiar shuffle of bags, passports, and jetlagged confusion. You will hand over your original passport, the vendor photographs it and sometimes takes a face photo, and you walk out with an active SIM. Airport kiosks are slightly more expensive than city stores but save you the hassle of finding a store once you’re out.

Official carrier stores in cities are the most reliable for registration and support, with wait times of 10 to 30 minutes. Avoid street vendors and small phone shops for your primary SIM — the registration process is often skipped or done incorrectly, which leads to deactivation.

eSIM

Viettel and Mobifone both support eSIM as of 2026, with Vinaphone’s eSIM service continuing to expand. You can purchase an eSIM plan online, receive a QR code by email, then activate it through your phone’s settings before you even board the plane. Third-party platforms like Airalo and Holafly also sell Vietnam eSIMs, though these function as roaming profiles rather than true local SIMs — fine for data, less ideal if you need a local number for app verification or hotel calls.

eSIM requires a compatible device. Check your phone model before purchasing. The activation process itself is straightforward: Settings → Cellular/Mobile Data → Add eSIM → scan the QR code. The catch is that you need a working internet connection to download the profile, so activate over hotel Wi-Fi if you haven’t already landed.

SIM Not Activating or Showing No Service — Step-by-Step Fixes

Your phone shows “No Service,” “Searching,” or zero signal bars after inserting the SIM. Here is what to check in order:

1. Restart the phone. Fixes a surprising number of network glitches immediately.
2. Check SIM seating. Remove the tray, reseat the card, reinsert carefully.
3. Select the network manually. On Android: Settings → Network & internet → Mobile network → Advanced → Network operators → turn off automatic and select Viettel, Mobifone, or Vinaphone. On iOS: Settings → Cellular → Network Selection → turn off Automatic → choose your carrier.
4. Check or set APN settings manually if data isn’t working after signal appears:

• Viettel APN: v-internet | Username: blank | Password: blank
• Mobifone APN: m-wap or internet | Username: m-wap or blank | Password: m-wap or blank
• Vinaphone APN: m3-world or internet | Username: mms or blank | Password: mms or blank

On Android, add a new APN via Settings → Network & internet → Mobile network → Access Point Names. On iOS, go to Settings → Cellular → Cellular Data Network.

1. Test in another phone to rule out a device-specific issue.
2. Return to point of purchase with your passport. If you bought at an airport kiosk or official store, they can verify activation and registration on the spot. If you bought from a street vendor, go directly to an official carrier store instead.

Slow Data or No Internet Connection — Diagnosing the Problem

Signal bars are showing and the 4G icon is visible, but pages won’t load or speeds crawl. This is a different problem from no service, and the fixes differ too.

1. Check your data balance first. Dial *098# for Viettel, *090# for Mobifone, or *111# for Vinaphone and follow the menu prompts. If your daily or total data cap is exhausted, no amount of troubleshooting will restore full speed — you need to top up or activate a new package.
2. Make sure mobile data is switched on. Easy to toggle off accidentally in quick settings.
3. Toggle Airplane Mode on for 30 seconds, then off. Forces the phone to reconnect to the tower.
4. Move location. Basements, thick concrete hotel rooms, and valleys can kill signal. Step outside or move to a higher floor.
5. Check the time. During major Vietnamese holidays — Tết being the obvious one — network congestion in city centers is real. The hum of millions of video calls happening simultaneously slows everything down. Wait it out or connect to hotel Wi-Fi.
6. Verify APN settings as described in the previous section.

For eSIM users specifically: confirm that Data Roaming is enabled for the eSIM profile under your cellular settings. Without it, data simply won’t flow even with a valid plan.

Can’t Make Calls or Send SMS — Balance Checks and Dialing Fixes

Many tourist data SIM packages include limited or no voice minutes. If you try to call and hear an automated Vietnamese message followed by a cut line, the most likely cause is zero main account balance rather than a network fault.

Check your main balance on any of the three carriers by dialing *101# and pressing call. If it’s empty, top up before trying again.

For dialing format issues:

• Domestic calls: Dial 0 followed by the 9-digit number — for example, 098xxxxxxx.
• International calls: Dial + followed by the country code and full number — for example, +1xxxxxxxxxx for the US.

If balance is sufficient and format is correct but calls still fail, visit an official carrier store with your passport. Incomplete SIM registration can trigger restrictions on voice and SMS while leaving data working — a confusing combination that often catches travelers off guard.

SIM Registration Problems — What Stricter 2026 Enforcement Means for You

Vietnam has required SIM registration since 2017, but enforcement through 2026 is the strictest it has ever been. The government’s stated goal is eliminating spam calls and SIM-based fraud. In practice, this means automated systems are actively scanning for SIMs registered to incorrect or mismatched passport data and deactivating them.

If your SIM was registered by a vendor who photographed a different passport or skipped the face photo step, you may find service suddenly stops working a day or two into your trip. The fix is not complicated but does require a trip in person:

1. Go to any official carrier store — Viettel Store, Mobifone Store, or Vinaphone Store. Find locations via the carrier websites listed above.
2. Bring your original passport. A photo on your phone is not accepted.
3. Explain that you need the SIM re-registered. Staff in tourist city branches typically speak enough English to handle this.
4. The process takes 15 to 30 minutes. There is usually no fee.

Running Out of Data or Balance Mid-Trip — Top-Up Methods

You have several ways to reload credit or activate a new data package without hunting for an official store:

• Scratch cards: Available at Circle K, FamilyMart, MiniStop, and most pharmacies. Scratch the panel to reveal the code, then dial *100*CARD_NUMBER# and press call.
• Carrier apps: My Viettel, My Mobifone, and My VNPT all allow top-ups and package purchases using a Vietnamese bank card or linked e-wallet. Download one of these immediately after activation — they are the fastest way to manage your account.
• E-wallets: MoMo, ZaloPay, and ViettelPay support direct top-ups for all major carriers. You typically need a Vietnamese bank account to fund them, though some allow cash loading at partner locations.
• Convenience store counter top-up: Walk up to the counter at Circle K or FamilyMart, give your phone number and the amount you want loaded, pay cash. Simple and reliable.

Once you have credit, activate a data package via the app or USSD. As a reference point, Viettel’s ST90N package in 2026 costs VND 90,000 (about $3.60) for 15GB over 30 days — activate by dialing *098# and selecting data packages from the menu, or through the My Viettel app.

eSIM Activation Problems — Device Checks, QR Codes, and What to Do Next

eSIM problems usually fall into one of three categories: device incompatibility, a failed QR code scan, or a profile that downloads but shows no service.

• Device not compatible: Check your model against the carrier’s eSIM compatibility list on their website before purchasing. Not all phones support eSIM, and some budget Android models still don’t.



• QR code won’t scan or has already been used: eSIM QR codes are single-use. If the scan fails or the profile doesn’t load, do not attempt to scan again from a screenshot — it may invalidate the code. Contact the provider (carrier or third-party like Airalo) to request a fresh code.
• Profile downloads but no service: You need a stable Wi-Fi connection during the download. If you activated over a weak hotel connection, the profile may be incomplete. Delete the eSIM profile from your settings and request a new QR code.
• For local eSIMs from Viettel or Mobifone: Visit a store or call carrier customer service. For third-party eSIMs, use the provider’s in-app chat or email support — response times vary.

2026 Budget Reality — Current SIM Package Prices

All prices below reflect 2026 projected tourist SIM packages. The exchange rate used is approximately 1 USD = 25,000 VND.

• Budget tier — Vinaphone Tourist SIM: VND 180,000 (~$7.20) | 30GB data (1GB/day) | 30-day validity | basic domestic call/SMS allowance
• Mid-range — Mobifone Tourist SIM: VND 200,000 (~$8.00) | 45GB data (1.5GB/day) | 30-day validity | limited domestic calls included
• Comfortable — Viettel Tourist SIM: VND 250,000 (~$10.00) | 60GB data (2GB/day) | 30-day validity | domestic calls/SMS included
• Add-on data only — Viettel ST90N package: VND 90,000 (~$3.60) | 15GB | 30 days | for existing SIM holders who need a top-up

The difference between the budget and comfortable tiers is roughly VND 70,000 — about $2.80. Given how much you will rely on maps, Grab, and messaging apps throughout a Vietnam trip, the Viettel package is the practical choice for most travelers, especially those going beyond major cities.

What Has Changed Since 2024

• SIM registration enforcement is significantly stricter. The crackdown that began accelerating in 2024 reached near-zero tolerance by 2026. Automated deactivation of improperly registered SIMs is now routine, not occasional.
• eSIM has matured. Both Viettel and Mobifone have streamlined their eSIM activation processes. Purchasing and activating a local Vietnamese eSIM online before travel is now genuinely easy compared to the patchy experience of 2023–2024.
• Digital top-ups are the default. Scratch cards still exist but carrier apps and e-wallets handle the bulk of recharges. The My Viettel and My Mobifone apps have improved significantly and are worth downloading immediately on arrival.
• 5G is expanding. Major urban areas — Hanoi, Ho Chi Minh City, Da Nang — have meaningful 5G coverage in 2026. If your phone supports 5G and you are in one of these cities, speeds are noticeably faster than the 4G baseline.



• Tourist SIM packages have grown more generous. Data allowances have increased year-on-year as carrier competition intensifies, making the tourist bundles better value in 2026 than they were in 2024.

Frequently Asked Questions

Do I need my passport to buy a SIM card in Vietnam?

Yes, and the original document is required — not a photo on your phone. The vendor will photograph your passport and may take a face photo for biometric verification. This has been mandatory since 2017 and enforcement is stricter in 2026 than ever before. SIMs registered without a valid passport are being deactivated by automated systems.

Which carrier has the best coverage in rural Vietnam?

Viettel is the clear choice for rural and remote areas, including mountain regions like Ha Giang and Sapa. Its network footprint extends further than Mobifone or Vinaphone in areas with sparse population. If your trip stays in major cities and coastal tourist towns, Mobifone is a solid and slightly cheaper alternative.

Can I use an eSIM in Vietnam instead of a physical SIM?

Yes, if your phone supports eSIM. Viettel and Mobifone both offer local eSIM plans as of 2026, which you can purchase and activate online before arrival. Third-party providers like Airalo also sell Vietnam eSIMs, though these are roaming profiles without a local Vietnamese number — fine for data, less useful for calls.

What should I do if my Vietnam SIM stops working suddenly?

The most common cause in 2026 is a registration issue — especially if the SIM was bought from an unofficial vendor. Go to any official carrier store with your original passport. They can check the registration status and re-register the SIM to your name. The process takes 15 to 30 minutes and is usually free of charge.

How do I check my data balance on a Vietnamese SIM?

Dial *098# for Viettel, *090# for Mobifone, or *111# for Vinaphone and follow the menu prompts. You can also check through the official carrier apps — My Viettel, My Mobifone, and My VNPT — which show remaining data, main balance, and package expiry dates in one screen.

📷 Featured image by Pham Hien Triet on Unsplash.