Your phone works on Wi-Fi, then apps, maps, messages, and web pages stop loading the second you leave it. That points to cellular data, SIM selection, roaming, VPN/profile routing, APN settings, or a carrier block. Start with the fast switches below, then move into the fixes that reset the mobile connection.
1. Turn mobile data on first
Start here if everything works on Wi-Fi and nothing loads on cellular. The phone needs mobile data enabled, and dual-SIM phones need the right line selected for data.
On iPhone: Open Settings > Cellular, then turn on Cellular Data. If you use multiple SIMs, open Settings > Cellular > Cellular Data, then choose the line for mobile data.
On Pixel and many Android phones: Open Settings > Network & internet > SIMs, then turn on Mobile data. For multiple SIMs, tap Mobile data under Your primary SIMs, then choose the data SIM.
On Samsung Galaxy: Open Settings > Connections > Data usage, then turn on Mobile data.
On Pixel and many Android phones, also open Settings > Network & internet > Airplane mode, then turn Airplane mode off.
2. Allow the app that fails off Wi-Fi
When one app works on Wi-Fi but stops on mobile data, check that app's cellular permission before changing carrier settings.
On iPhone: Go to Settings > Cellular, scroll to the app list, tap Show All if needed, then turn cellular data on for the affected app or service.
On Samsung Galaxy: Go to Settings > Connections > Data usage > Allowed networks for apps, tap the app, then select Mobile data or Wi-Fi or Mobile data preferred.
On Pixel and Android: Open Settings > Network & internet > Data Saver, then turn Data Saver off. To keep Data Saver on, open Unrestricted data, then turn on the affected app or service.
3. Remove data limits and account blocks
Samsung data limit: Open Settings > Connections > Data usage > Billing cycle and data warning, then turn off Set data limit.
Samsung Data saver: Open Settings > Connections > Data usage > Data saver, then turn Turn on now off. To allow one app through, tap Allowed to use data while Data saver is on, then turn on that app.
iPhone Screen Time: Open Settings > Screen Time > Content & Privacy Restrictions > Allow Changes, then allow cellular data changes.
Carrier controls block data at the account level too. AT&T account holders can sign in to the wireless usage summary, select the line, open Data > Manage data usage, then turn Cellular Data on.
Verizon users can open My Verizon > Mobile > Settings & preferences > Block specific services, then turn off the relevant service block.
Verizon Family users can open Family Profiles > Parental Controls > Restrict usage > Data limits, then adjust the line's limit.
4. Enable roaming when you travel
Outside your carrier's home coverage area, cellular data usually needs roaming enabled on the phone and allowed by the plan.
On iPhone with one SIM or eSIM: Go to Settings > Cellular or Cellular Data, turn on Cellular Data, open Cellular Data Options, then turn on Data Roaming.
On iPhone with Dual SIM or Dual eSIM: Go to Settings > Cellular, turn on Cellular Data, tap the number to modify, open Cellular Data Options, then turn on Data Roaming. Also tap the cellular line and enable Turn On This Line.
On Pixel and many Android phones: Open Settings > Network & internet > SIMs, then turn on Roaming.
On Samsung Galaxy: Open Settings > Connections > Mobile networks, then turn on Data Roaming or Data Roaming Access.
T-Mobile travel check: Dial #WEB# to check data use, data plan, or expiration. Dial #RON# to turn international data roaming on, or #ROF# to turn it off.
5. Restart and reseat the SIM
A restart clears active network processes and forces a fresh mobile connection.
On iPhone X or later: Hold the side button and either volume button until the power-off slider appears, drag the slider, wait 30 seconds, then hold the side button until the Apple logo appears.
On iPhone 6, 7, 8, or SE 2nd or 3rd generation: Hold the side button until the slider appears, drag it, wait 30 seconds, then hold the side button again.
On Pixel: Power the phone off, wait 30 seconds, then turn it back on. You can also toggle Airplane mode on and off to shut down active processes.
On Samsung Galaxy: Swipe down from the top right corner twice, tap the Power icon, tap Restart, then tap Restart again.
If your phone uses a physical SIM, open the SIM tray with a SIM-eject tool or paper clip, remove and inspect the SIM, place it correctly in the tray, then reinsert the tray fully.
For iPhone eSIM, open Settings > Cellular > Set Up Cellular or Add eSIM, then use the activation option offered by your carrier.
6. Update carrier settings and software
iPhone carrier settings: Connect to Wi-Fi, then open Settings > General > About. If a carrier settings update appears, follow the onscreen instructions.
iPhone software: Open Settings > General > Software Update. If an update is available, tap Download and Install, then follow the onscreen instructions.
Android software: Open Settings > System > Software updates or Software update, then follow the onscreen instructions.
7. Disconnect VPNs and repair APN settings
VPNs, configuration profiles, APN settings, and network selection control how mobile traffic leaves the phone. Fix those next.
On Android: Open Settings > Network & internet > VPN. Tap Settings next to the VPN, then turn it off or tap Forget. Also turn off Always-on VPN and Block connections without VPN.
On iPhone: Open Settings > General > VPN & Device Management, select the profile, tap Delete Profile or Remove Profile, then restart. On managed school or work phones, contact the organization that controls the device.
On iPhone APN: Go to Settings > Cellular > Cellular Data Network > Reset Settings. Use manual APN edits only when your carrier or mobile device administrator gives you the values.
On Pixel and many Android phones: Open Settings > Network & internet > SIMs > Access point names, then verify the carrier APN. Use SIMs > Network to verify the network operator where available.
On Samsung Galaxy: Open Settings > Connections > Mobile networks > Access Point Names, then verify the carrier APN. Go back once to Network operators, then turn on Select automatically.
8. Reset mobile network settings
Use this after the switches, SIM checks, updates, VPN, and APN checks are done. A network reset clears broken mobile settings. On iPhone, it also removes saved Wi-Fi networks and passwords, cellular settings, VPN settings, and APN settings.
On iPhone: Open Settings > General > Transfer or Reset [device] > Reset > Reset Network Settings.
On Pixel: Open Settings > System > Reset options > Reset mobile network settings.
On Samsung Galaxy: Open Settings > General management > Reset > Reset mobile network settings > Reset settings > Reset.
Use the paths above. Older iPhone guides list Settings > General > Reset > Reset Network Settings, and older Android guides list a combined Wi-Fi, mobile, and Bluetooth reset. Those are legacy paths, not the current Apple and Pixel support paths.
9. Ask the carrier to check the line
If the phone settings are correct and mobile data still fails, the carrier needs to check the line. Ask support to confirm no outage, an active data plan, no data block, correct SIM or eSIM provisioning, correct IMEI, and roaming permission when traveling.
Pixel shortcut: Open Settings > Network & internet > Troubleshoot mobile connection before calling.
T-Mobile travel check: Use T-Mobile's international roaming checklist to search the destination country, enter the device, click Check coverage, then review device compatibility, active roaming blocks, and line status.
Frequently Asked Questions
Why does my phone work on Wi-Fi but not cellular data?
Mobile data is off, the wrong SIM is selected for data, one app is blocked, Data Saver is restricting traffic, roaming is off while traveling, a VPN or profile is routing traffic incorrectly, APN settings are wrong, or the carrier has a block or provisioning issue on the line.
Why do only some apps work without Wi-Fi?
Those apps are blocked from using cellular data or restricted by Data Saver. On iPhone, check the app list under Cellular. On Samsung, check Allowed networks for apps. On Pixel and Android, turn off Data Saver or allow the app under Unrestricted data.
Will resetting network settings delete my photos or apps?
No. These vendor reset steps reset network settings, not the phone's content. On iPhone, the reset removes saved Wi-Fi networks and passwords, cellular settings, VPN settings, and APN settings. Samsung notes that customized APN settings need reconfiguring after its mobile network reset.
Should I change my APN settings manually?
Use manual APN edits only when your carrier or mobile device administrator gives you the exact values. On iPhone, use Reset Settings on the Cellular Data Network screen when that screen is available. On Pixel, Android, and Samsung, verify the carrier APN instead of guessing new values.
What should I ask my carrier to check?
Ask the carrier to confirm no outage, an active data plan, no data block, correct SIM or eSIM provisioning, correct IMEI, and roaming permission if you are traveling.