Once in awhile our apple products can turn out to have uncommon problems which most times keep us puzzled. Some of these errors can only be dealt with by experts. sometimes we have to figure it out on our own.
recently an iPhone SE ran into a different type of problem. the phone lost signal, sim card did not read and calling was not allowed.
in case your phone isnt reading the sim and has no network coverage you could try to
- Remove the sim and try another one.
- Update software
- Backup and Factory reset
Failing with all of the above it would be ideal to
- Get a genious opinion
- Visit the apple store for solution
Incase you purchased or are using a second hand phone try checking if the phone is completely unlocked to be able to use any carrier. also check if the sim and carrier supports the iphone. sometimes the phone may work for sometime and later freeze and face such of the above problems if sim is not supported by carrier or the phone itself isnt properly registered.
if none of the above helped, it could be that the previous user cancelled the plan without paying the complete price for the phone and while being resold the second buyer was slammed with such issues as the above.
A cancelled IMEI number could be behind all this inconvenience. Please double check all of the above before purchasing a second hand phone.
best of luck