At&T Tilt or Iphone PDA data plan question. Do i have to purchase a data plan to it?

[wzzp144]

I am willing to purchase a phone either Iphone or At&t Tilt. I maybe buy it from ebay. Now do i have to purchase a data plan thing for $30 dollars even tho im not willing to use the internet alot? I have wifi on them. When i activate the phone do i have to purchase the data plan? i really do not want to. im going to add this on the family plan.

[?? wälkïn.ön. §ün§hïnë™??]

You have to get the data plan if you get the iPhone. There's no way around that. If you get the Tilt though, you don't necessarily need to buy the data plan. =]