Sim not supported issues

If you can't activate your iPhone - Apple Support

Your phone is network locked and won't allow other network sims to work.

You need to have the original sim onboard and then contact the operator to have the phone unlocked before a different sim can be used.

You also need to be the subscriber of the original sim and bill payer to make the unlock request.

If you bought the phone used and it was network or Apple ID locked afraid you have a brick from the perspective of a phone.