My landline can't call my cellphone...
When either of my two legacy landlines in my house try to call by daughter's cellphone, we get the message that her line has been "disconnected or is no longer in service." My next door neighbor also has an ATT landline, and she gets the same error message when she calls my daughter's cellphone.
My daughter can receive calls from everyone, and she can even call the landlines that can't call her.
We went to the ATT store and they took the SIM out of her phone and put it into one of theirs, and we tried to call from our landline...still the same problem. Then they gave us a new SIM, and we tried to call again from our landline...still the same problem. So, that proves that neither her cellphone or her SIM are the culprit.
We think it must be the landlines somehow, now, but the people that I call at ATT are baffled. They haven't sent anyone out yet, preferring to try to make it work from their end...so far no luck.