How much can an Apple Store do on AT&T Accounts/Adding Line to existing Family Plan

I'm prepared to get two iPhones this friday. The first one is just upgrading an upgrade eligible line. The second one I want to do is porting a number from another account on T-Mobile to my AT&T Family plan to add onto it as an additional line. Is the Apple store capable of doing this much work (porting/adding lines/managing a family plan)?

I'm really just trying to avoid the AT&T store. The employees are usually rude and it takes way longer. I try to stay away if possible.

If anyone knows the answer I'd be very grateful!
Steve

OKAY, I finally got the time to go and check with Apple about this. He said Apple stores cannot change service, deal with family plans, or port phone numbers. Seems a little ridiculous to me, but I guess I will have to go to AT&T tomorrow 😡

Steve