update on this - apple 'genius' says that this is a modem issue and can't be repaired and she'll need to buy a new phone. sounds like bullshit to me.
What version does it have on it currently?
It should support iOS 12, so if the phone has anything less than 12.1 (or 12.2, but that was only out yesterday) then it should be able to be updated.
Connect to a computer/iTunes, download iOS from there and do an update/restore?
Maybe backup what you need and completely wipe and start again with updated OS...
it updated to the latest iOS (well 12.something) then this happened. The suggestion by apple that it's a physical problem seems to be a very convenient!
Now its up to date, but apparently needs a (possible according to google) cellular carrier update.
Its on giffgaff, maybe I'll try them.
What version does it have on it currently?
It should support iOS 12, so if the phone has anything less than 12.1 (or 12.2, but that was only out yesterday) then it should be able to be updated.
Connect to a computer/iTunes, download iOS from there and do an update/restore?
Maybe backup what you need and completely wipe and start again with updated OS...
(haven't read through this guide but a quick scan looks sensible - https://www.gottabemobile.com/how-to-do-a-clean-ios-12-install/)