Verify and ensure cellular data is enabled on your iPhone
Check to see if your iPhone has cellular data turned on.
Some iOS upgrades will automatically reset some of your device's settings, requiring you to adjust them. As a result, double-check that your iPhone's cellular data is turned on. Navigate to Settings->Cellular to do so. Toggle the On/Off button to activate cellular data on your smartphone if necessary. To connect to a cellular network, your iPhone must have cellular data turned on.
Reset Network Settings.
This network problem can also be resolved by resetting the network settings to factory defaults. The procedure will assist you in removing small issues with your iPhone's network operation.
To do so, go to Settings-> General-> Reset->Reset Network Settings on your iPhone. The procedure will reset your Wi-Fi networks and passwords, as well as your cellular settings, VPN and APN settings, and any other previously used settings. As a result, be certain to back up this information before you begin.
