Hi I passed on my S9 to my daughter, I had it for a year and switched to a Pixel and she had an older S7. I factory reset it and then moved her stuff in (she's special needs). I've come to find out that since I gave it to her, she cannot receive any calls. She can call out. She can send/receive texts from everybody. The house landline can call her. The rest of us get a please check number and try again. I went to AT&T store and they spent an hour with me, even changed out her SIM card. They ended up escalating the issue (tried everything). I got home and being tech support myself, I swapped her SIM card for mine, and put hers in my Pixel. I could call her number/my phone, she could call my number/her phone. No one else could call her number (so in my opinion, that takes the phone out of the equation). I swapped the cards back to their respective phones and now I could call her!! So the landline can call, I can call. Dad, and several staff cannot. Come to find out, they all (4 of them) have iPhones, 3 are on AT&T, one is on Sprint. I also asked my other kids to call her as they don't have iPhones, and alas, they cannot, so that's not it. I spent over and hour yesterday and another hour today with AT&T chat and escalated tech support. They truly have no idea. Her phone has been factory reset 4 times now, she essentially has NO apps on it as I haven't set it up again. No calls are blocked, all numbers are in her list/contacts. I am truly at a loss and so is AT&T. I've looked all over the internet, I've tried everything; cleared network cache, reset 3x, checked all settings. Any suggestions from here? AT&T could also call her but the call got rejected because it was from an unknown number. Thank you.
This sounds to me like it's her Mobile Network Account that's at issue.
Networks can reset / flush out accounts.
Current Phone ~
Samsung Note 20 Ultra 5G SM-9820 _ Samsung One Ui 2.5/ Android 10. Snapdragon 865+