need to change mobile services

Hello.

I want to change my Service to Xfinity Mobile.  I just hate when Straight Talk turns my service off after the 1 year contract.  It clearly says in their advertisement if you have auto pay it will auto renew but it does not.

How do i change my service TODAY when the local store is closed.  I dont want to wait a week or what ever.  I need my phone now.  If i have to wait i may as well sign up for another year with them.

Mary