Phone Unlocked But Still No Service? 10 Fixes That Work (2026)

You did everything right: the carrier approved the unlock, or you bought a phone sold as unlocked. You insert a new SIM — and the status bar says No Service, Emergency calls only, or shows full bars with no data. It’s one of the most frustrating situations in mobile, because the phone looks fine and the problem is invisible.

The key insight: an unlock only removes one barrier — the carrier policy. The phone still has to register on the new network, which depends on radio bands, network technology, settings, the network’s own rules about which devices it accepts, and the IMEI itself. Work through these ten fixes in order; they go from quickest to most involved.

Before you start: confirm the unlock actually took

Many “no service” cases are simply phones that are still locked. On an iPhone, open Settings › General › About › Carrier Lock — it must say “No SIM restrictions”. On Android, a locked phone usually asks for a “SIM network unlock PIN” when a foreign SIM is inserted. If you have any doubt, a carrier + SIM-lock check or a SIM-lock status check reads the status by IMEI. Our guide to checking if an iPhone is unlocked covers the details.

If the phone is locked, nothing below will help — and if it says “SIM Not Supported” rather than “No Service”, read SIM Not Supported on iPhone instead.

Fixes 1–3: The quick resets

1. Restart and toggle airplane mode

After a SIM change or an unlock, the modem can hold on to its old registration. Turn on airplane mode for 30 seconds, turn it off, then restart. On an iPhone that was unlocked recently, the restart with the new SIM inserted is also what triggers re-activation with the new policy.

2. Install the carrier settings update

On iPhone, go to Settings › General › About and wait about 30 seconds on Wi-Fi. If a carrier settings update exists for the new SIM, a prompt appears. Install it — it carries network-specific configuration such as VoLTE and 5G profiles. On Android, carrier configuration usually arrives through system updates and Google Play system updates, so install any pending ones (Settings › System › Software update, or Settings › Software update on Samsung).

3. Reset network settings

• iPhone: Settings › General › Transfer or Reset iPhone › Reset › Reset Network Settings.
• Pixel: Settings › System › Reset options › Reset Wi-Fi, mobile & Bluetooth.
• Samsung: Settings › General management › Reset › Reset network settings (or Reset mobile network settings).

This clears saved Wi-Fi networks and VPN profiles but no personal data. It removes stale APN entries and network preferences that came from the old carrier.

Fixes 4–5: APN and network mode

4. Set the correct APN

If you have signal and can call but there’s no mobile data or MMS, the APN (access point name) is almost always the culprit. Unlocked phones from another country often don’t recognize the new carrier and pick no APN at all.

• Android: Settings › Network & internet › SIMs › (your SIM) › Access Point Names (Samsung: Settings › Connections › Mobile networks › Access Point Names). Tap “+”, enter the carrier’s published values, save, and select the new APN.
• iPhone: Settings › Cellular › Cellular Data Network appears only for carriers that allow editing. Most carriers configure it automatically through the carrier settings update.

Get APN values from the carrier’s official support pages — not from random lists, which are often outdated.

5. Check the preferred network type

Many countries have switched off 3G and some are retiring 2G. A phone left on “3G only” or “2G only” will show no service. On Android, go to SIM settings › Preferred network type and choose the option that includes 5G/LTE. On iPhone, Settings › Cellular › Cellular Data Options › Voice & Data should be set to LTE or 5G Auto. Also check that VoLTE / 4G Calling is enabled — on 3G-free networks, calls depend on it.

Fix 6: Make sure the phone supports the network’s bands

An unlock doesn’t add radio hardware. A phone built for one region may lack the LTE or 5G bands your carrier relies on, especially in rural areas where low-frequency bands carry coverage. Symptoms: signal in cities but nothing outside, or 4G that drops to no service.

Identify the exact model first — on Android, the model code in Settings › About phone; on iPhone, the A-number from Settings › General › About › Model Number. A manufacturer + model check or, for Galaxy phones, a Samsung info report confirms the variant from the IMEI. Then compare its band list on the manufacturer’s spec page with the bands your carrier publishes.

Fix 7: Device acceptance, IMEI registration and VoLTE whitelists

Some networks only allow devices they have certified, especially for VoLTE and Wi-Fi calling. If the phone isn’t on the list, it may get data but no calls, or no service at all. Many carriers have an online compatibility checker — enter the IMEI there.

Some countries also require imported phones to be registered by IMEI with a national system before local networks will serve them; unregistered phones can work briefly and then stop. If you brought the phone from abroad, check the rules of the country you’re in. Travelers with US phones should also read using a US iPhone abroad.

Fix 8: Check the blacklist

An unlocked phone can still be blocked by IMEI. When a phone is reported lost or stolen — or flagged for an unpaid balance in some markets — networks that share the report refuse to register it. The typical symptom is a SIM that’s accepted, then No Service on every network.

Run a GSMA blacklist check for international reports and a USA blacklist / barred check for US carrier flags.

Fix 9: Restore and re-activate

For iPhones, a full restore forces a fresh activation with Apple, which also applies the current carrier policy and resolves corrupted baseband settings. Back up first, then restore with a Mac (Finder) or PC (Apple Devices or iTunes) — a computer restore reinstalls iOS and the modem firmware, which an on-device erase doesn’t always do.

For Android, a factory reset after backing up can clear corrupted carrier configuration. Make sure you know the Google account on the phone first, or Factory Reset Protection will lock you out after the reset — see how to factory reset a phone properly.

Fix 10: IMEI missing, null or invalid

Dial *#06#. If the IMEI is blank, all zeros, shows “null” or doesn’t match the box, the network cannot register the phone. On iPhone, a missing IMEI usually points to a baseband (modem) hardware fault. On Android, it often follows a bad firmware flash, a corrupted modem partition (sometimes called EFS or NV data) or a board repair.

The legitimate fix is reflashing official firmware or a board-level repair by the manufacturer or an authorized service center. Writing a different IMEI to a phone is illegal in many countries and is not a fix.

On Android, you can read the modem state with ADB (developer options and USB debugging must be on). If the IMEI is present but you want to know what records say about it, the IMEI check page lists every report by brand. These three commands show the modem’s state:

adb shell getprop gsm.version.baseband
adb shell getprop gsm.sim.state
adb shell getprop gsm.operator.alpha

An empty baseband version points to a modem or firmware problem; a SIM state of READY with an empty operator means the SIM works but the phone isn’t registering — look back at bands, network mode and blacklist status. Want to verify the IMEI digits themselves? In the terminal below, type imei followed by the 15-digit number and press Enter.

Diagnose it in two minutes

Start with the IMEI — it answers the lock and blacklist questions at once: