Sounds like you've moved around, and your phone has lost its signal (it'll still show full signal in bars).
Turn off the handset.
Remove the SIM card
Wait 1 min
Replace SIM card (give it a wipe if you wish)
Turn phone back on
... Hopefully that's it sorted.
It happens, especially if your on O2.
Sometimes if you've moved around, your phone gets lost in the various network signals, and you have to reboot it again.... Good news, no factory reset, just signal reset.
.....
If I helped or solved your problem, please like or tick solved.
Have been using phones since 1993, and am self taught.
I offer advice for free, cos I think it'll help, if it doesn't, explain why, I might learn something new too.
Current phone Galaxy S22 Ultra
Previous phones: most S series, Note 2, Samsung Alpha, iPhone 3gs, far too many Nokia's!
