I am trading in a 5S for a new iPhone 7. I am wondering if I transfer the new iPhone (once I receive it) to one of my existing lines (which is still under contract),will it void the $400 credit that I will be receiving (over 24 months)? I'm basically hoping to add a line with the new phone, but then switch lines once it arrives. Both lines will be in the same account. Just wondering if this will cause the monthly credits from the trade in to stop. Does anyone know?