I have noticed when traveling between regions (usually Dunedin to Wanaka) I lose the data connection on my mobile phone (Oppo AX5 2019, buildnum CPH1851NZ_11_A.22 baseband Q_V1_p14 ) even though it appears to have strong signal.

A recent example of this is we traveled from Dunedin to Middlemarch to camp for new years, once we we arrived I had 4 bars of reception but the 3g indicator was missing and I could not use services that require data (didn't check sms or calling). Restarted phone and the 3g indicator was back along with a working data.

This issue doesn't worry me, I'm more curious of what/why this might happen.