My son's iPhone has suddenly stopped having internet connectivity outside of the house.  All the apps say there isn't an internet connection to use.

I wondered if there are any things I can try before I having to find and go into a One NZ shop (the forums seem to strongly suggest not calling the help line...).   Ideas, or things I can post here to give you more info to help diagnose it?

I have the One NZ app on my phone and he definitely has data available, and OneNZ doesn't cap your data when you run out anyway it just bills you for data usage over your limit.

His internet works fine over wifi or if he connects to my phone's hotspot.

If I go into the mobile data settings I can see a list of fields that contain info like APN and MMSC etc   Are there things here to check?  Oddly when I check mine (I am 2degrees) I dont have any username or passwords in these fields, but his do for some.

All help appreciated.

EDIT: have tried turning it off and on again