Romaing disconnected - data and incoming sms work fine

[Ma2021]

I am currently abroad in eastern Europe (Prague) and while connected to the local O2 brand network it is impossible to stay registered with the network. Incoming sms and 4G data work just fine, just outgoing and incoming calls and outgoing sms do not work. When a call is made the network gives a busy tone. When you manually select a different network and then reconnect to O2 then all works fine for about 5 minutes.

So far I have tried 2 different phones, one brand new one, turn off/on, airplane mode, manual roam - select a different provider, tested different cities, also have a giffgaff number with me that uses O2 network with the same result.

Any ideas much appreciated.

Cheers

[pgn]

Try switching your phone from 4G to 3G/2G, @Ma2021 Guide: What is 2G, 3G, and 4G? 

Worth a shot.

[Ma2021]

Thanks, tried that too but no success. The phone does indicate that it is registered with local O2 network, however outgoing and incoming calls and outgoing sms do not work at all.

[MI5 · Accepted solution]

@Ma2021 

Some things to try.
1 - Manually search for a different network.
2 - Reboot your phone
3 - Call customer service to check for any roaming bars.
4 - If using an iPhone, change data apn to "mobile.o2.co.uk"