on 19-10-2020 12:16
on 19-10-2020 12:19
Have you checked here O2 Service Status ?
Or reported issue through My Network app https://www.o2.co.uk/apps/my-network
on 19-10-2020 12:22
on 19-10-2020 12:25
on 19-10-2020 12:25
Unfortunately faults do happen and need to be fixed.
Can you use wifi calling in the meantime ?
https://www.o2.co.uk/connectivity/wifi-and-4g-calling