I'll post this one more time (the OP should add it to his message): Try this: Settings > Mobile Data > Network Selection Disable "Automatic" Select your mobile network manually Restart the iPhone After that, try to toggle airplane mode and check if the mobile network connection still works.

I will repost this because it seems almost nobody reads the older messages: Steps: Settings > Mobile Data > Network Selection Disable "Automatic" Select your mobile network manually Restart the iPhone After that, try to toggle airplane mode and check if the mobile network connection still works.

@Sebsid if you want to try my workaround you should select the network that allows you to make phone calls. All the phone calls are made through the 3G bands unless your carrier supports VoLTE (voice over LTE) on roaming, that's why it goes from 4G to 3G when you make or receive a call. There are 4 mobile networks operating in Spain: Movistar, Vodafone, Orange and MasMovil (Yoigo/Xfera), but only the first three support the lower bands (800 Band 20 (EUDD) and 900 Band 8 (E-GSM)).

I think I have found a workaround, try this: Settings > Mobile Data > Network Selection Disable "Automatic" Select your mobile network manually Restart the iPhone After that, try to toggle airplane mode and check if the mobile network connection still works.

I suffer this critical bug too, it's related with the 4G/LTE signal exclusively. I've found a way to reproduce it every time. When you have the mobile data enabled and working you can force the bug by simply enabling airplane mode. Then, when you disable airplane mode, you will lose your 4G data connection. When the phone tries to reconnect it does not get a working APN IP address from the cell tower. You can check it here: Go to Phone > Keypad Call *3001#12345#* PDP Context Info > 0 Check IPv4 (or IPv6) field If you see "0.0.0.0" instead of a regular IP address, then you don't get a data connection with the cell tower. That's why you get mobile signal but you can't access the Internet. In other words, you still get access to the cell tower but you don't get a working IP from it. Sometimes it gets solved with a soft reset (turn off, turn on, enter your SIM password if any), but sometimes you have to try several times until it works again. iOS 14.0.1 iPhone 6s Spain Carrier: Jazztel (Orange brand and mobile network)