❓ Why “Roaming ON” Still Shows No Service

Turning roaming ON is necessary for many travel plans—even when you are already in Vietnam. But roaming alone doesn’t fix everything. The most common reasons for No Service or “bars but no internet” right after landing are:

• Wrong network picked (device stayed on a foreign network or latched to a partner it can’t use).
• APN not provisioned (the data profile didn’t auto-fill, or an old APN is still active).
• Dual-SIM priority conflict (data line quietly set to your home SIM after reboot).
• Outdated carrier bundle (phone needs a quick reset to fetch the local settings).
• Physical SIM vs eSIM order (some phones behave better when you disable the unused line during setup).

Good news: most cases resolve in a couple of minutes with the steps below. Start with the quick path that matches your phone.

🧭 Quick Checks Before the Deep Fix

• Data line: set the Vietnam line (eSIM/SIM) as your Cellular Data line. Home SIM can stay for calls if you like, but make sure data points to the Vietnam line.
• Roaming: ON for the Vietnam line if your plan requires it. Many travel eSIMs need roaming enabled even inside Vietnam.
• Airplane Mode: ON for 10–15 seconds, then OFF to force a clean registration.
• Manual network (one-time): turn off Automatic and choose Viettel, MobiFone, or VinaPhone depending on your plan. After it connects, you can return to Automatic.

🍎 iPhone Steps (iOS 16–18)

1. Data line: Settings → Cellular/Mobile Data → Cellular Data → select your Vietnam line.
2. Roaming: Settings → Cellular → your Vietnam line → Data Roaming ON.
3. Manual network pick (once): Settings → Cellular → Network Selection → turn OFF Automatic → pick the carrier your plan uses (Viettel/MobiFone/VinaPhone).
4. Reset Network Settings (if still offline): Settings → General → Transfer or Reset → Reset → Reset Network Settings. Your phone restarts and forgets saved Wi-Fi (you’ll re-enter later).
5. APN check: Settings → Cellular → your Vietnam line → Cellular Data Network. If empty after the reset, add the APN “Name” from the table below (leave other fields blank).
6. Final nudge: toggle Airplane Mode 10 seconds after any change.

🤖 Android Steps (Samsung / Pixel / others)

1. Data line: Settings → Network & Internet (or Connections) → SIMs → set the Vietnam line as the data SIM.
2. Roaming: Settings → Mobile network → Data roaming → ON for the Vietnam line.
3. Manual network pick (once): Settings → Mobile networks → Network operators → OFF Automatic → select the local carrier allowed by your plan.
4. Reset APNs: Settings → Mobile Network → Access Point Names → menu (⋮) → Reset to default.
5. Add APN (if needed): Access Point Names → Add → enter only the APN “Name” from the table below → Save → select it.
6. Final nudge: Airplane Mode ON 10–15 seconds, then OFF.

📋 APN Names You May Need (Vietnam)

If your phone didn’t auto-provision after a reset, fill APN (Name) only and leave other fields blank unless your device insists:

📶 Dual-SIM Gotchas to Watch For

• Wrong priority: after a reboot, some phones flip data back to your home SIM. Always re-check the data line.
• Disable the unused line temporarily: while you test the Vietnam line, turn the other SIM OFF to reduce conflicts. You can turn it back ON after data is working.
• Visual confusion: bars on the status bar don’t guarantee data. Open a simple webpage (example.com) to confirm.

⏱️ First-Hour Fix You Can Do at the Airport

1. Set Vietnam line as Cellular Data line; keep your home SIM for calls if needed.
2. Turn Data Roaming ON (if your plan needs it).
3. Pick the local network manually (once). If registration succeeds, switch back to Automatic.
4. Reset APN to default. If no data after 60 seconds, add the APN from the table.
5. Toggle Airplane Mode for 10 seconds. Try loading a lightweight page.
6. Reboot once if speeds are stuck under 1 Mbps despite strong signal.

For a step-by-step airport checklist (including battery and QR prep), see the pillar: Airport First-Hour Playbook.

🧪 Three Short, Real Cases

Case A — iPhone 13 at SGN (Ho Chi Minh City)

Symptom: Roaming ON, 4 bars, but no data. Fix: Reset Network Settings; APN auto-provisioned; data returned in ~30 seconds. Likely cause: stale APN from a previous regional eSIM.

Case B — Galaxy S21 at HAN (Hanoi)

Symptom: Roaming ON but “No Service” after landing. Fix: Manual network pick to Viettel; add APN v-internet; Airplane Mode 10 seconds. Outcome: 50–90 Mbps downtown. Note: device had two eSIMs and defaulted data to the wrong one.

Case C — Pixel 7 at DAD (Da Nang)

Symptom: Stuck on LTE with < 1 Mbps. Fix: One manual pick to VinaPhone; APN m3-world already set; a reboot restored normal speeds. Note: Pixels sometimes need one manual selection after landing.

💵 What People Pay: Airport Counter vs. Online eSIM

🧯 When to Escalate (and What to Tell Support)

• Still No Service after all steps? Share your device model, iOS/Android version, your eSIM/SIM provider, and the carrier your plan is supposed to use.
• Send a screenshot of the SIM Manager (showing enabled lines), Network Selection page, and APN screen.
• Try a different location in the terminal (rare, but dead spots exist), and confirm not in airplane mode by mistake.
• Switch to another allowed carrier (if your plan supports more than one) and retest after an APN reset.

💡 Quick FAQ

Do I have to enable roaming inside Vietnam? Many travel eSIMs require Data Roaming ON to work, even domestically. If in doubt, keep it ON while in Vietnam.

Will editing APN break calls or OTP? No—APN is for data. If your plan includes a VN number, you may need a small top-up for voice/SMS. Data-only plans do not place cellular calls/SMS, but you can use WhatsApp/LINE/WeChat over data.

It shows 5G but speed is slow. Bars don’t equal throughput. Try a manual network pick once, toggle airplane, then reboot. If your plan has a daily high-speed allowance, check today’s usage.

My phone has many eSIMs saved. Delete old ones you no longer use or disable them. Too many inactive profiles can confuse some devices during registration.

📣 Get Online Without the Guesswork

Start with the full airport checklist so you’re ready before immigration: Open the Vietnam Airports eSIM First-Hour Playbook

Prefer to set up now? Explore Vietnam-wide eSIM options with instant QR delivery: Vietnam eSIM 30-Day plans

📞 Support

WhatsApp +84 98 307 49 15 · LINE: anyaxiaoying · Email: info@govnsim.com

Part of Heera Travel Group – Explore more Vietnam tours at HeeraTravel.com.