I just called AT&T, because I had a question about whether changing your credit card information will in any way affect your ability to keep your unlimited data plan. (Answer: It won't.) While I was on the phone with them, I asked specifically, "What would I have to do in order to LOSE my unlimited data plan?" The answer I received is that you would have to click CANCEL PLAN and cancel your data plan, or drop down to a lower data plan, in order to lose the unlimited data plan. Changing your credit card info, billing or service address, etc. will NOT cause you to lose the unlimited data plan, according to the AT&T rep. So: DON'T CLICK "CANCEL PLAN". Also: If you get a new iPad, the procedure to follow is to call AT&T and have them transfer your unlimited data plan from the old iPad's SIM number and IMEI number to the *new* iPad's SIM number and IMEI number. If you do this, you can transfer your unlimited data plan. Hope this helps!