Trying to switch from a relative's plan to my own

I am currently under my mother in laws mobile plan with Xfinity. I want to get my own, and I have the deal for a free year. Me and my wife both have service through her. I want to switch, but I just want to see if I can still get the deal, or if there will be an issue. I tried doing it online and it gave me an error and said to try again later. 

I want to keep our current numbers, and I don't want her to release them if there will be an error activating phones on Xfinity that are being transfered to another Xfinity plan.

Thank you.