Going with the NEXT plan, paying full price up front or Apples subsidized plan does not change your unlimited grandfather plan. But I believe in actual fact you will be paying a lot more in the long run. Your ATT plan already has a built in charge if you will. When we all sign up for the 2 year contract and we pay $199/299/399 I'm sure the remaining balance is built in to our normal ATT billing.
So it was confirmed you lose unlimited data if you do 2 year contract? I'm switching to T-Mobile because I don't want to be forced into pre-ordering with AT&T from now on due to only their site having the 2 year contracts.
However, I just tested it out. I pretended I was going to upgrade my eligible line to the 6 Plus. The Express checkout doesn't ask you anything about changing your plan, they only try to sell accessories and insurance.
Why would you lose your data plan? The order form I just tried has nothing about changing your voice or data plan.