Iphone 8+ will not activate - T-Mobile

I purchased an iphone 8+ for my granddaughter. She is in Kansas, I am in California. The account is in my name. I pay the bill. She is replacing a 6+. When she attempts to set up/activate the 8+ she is asked for the last 4 of my ssn. It will not accept that. Says cannot verify. She then went to the T-Mobile store. They took a new sim and copied info from old. Still does it. They have "never seen this before". Sent her to Apple Store. Apple store reset the phone via itunes and they get same message. The last 4 on ssn is correct in the account. Apple said new phone will do same thing if she exchanges it. So, she goes home and gets on phone with T-Mobile tech and he can't figure it out. He then connects to Apple tech. They have never seen this before. TMobile leaves conversation. Apple tech sends her to Apple Care....she was then cut off.

So, does anyone have ANY IDEAS? Please don't say change carriers, buy Android, etc. It's a 60 mile round trip to either Apple or TMobile. It sure would be nice if someone here can solve it, or at least tell us what to do. ......

Thank you very much

Sandy