Can I use unlocked iphone on existing ATT Data Plan?

[Snakedoc]

I have a data plan with ATT already and was wondering if I could buy an unlocked iphone 3g and use it on my already existing data plan.

I've read on forums that ATT can detect when an iphone is being used on a plan other than the iphone plan and if they do, then they charge your bill for the 30$ iphone plan...is that True?

Basically I want to know if I can get an unlocked iphone working on my existing data plan with no problems with the phone or ATT.
my data plan is unlimited...its the unlimited text and data plan for $30/month.

will the iphone work on this data plan?

[iOWN77]

yes i did it you just have to add unlimited data plan

[Desiree]

You can certainly use the iPhone with your ATT service but the $30 per month iPhone data plan is a requirement. The current data plan you have will not be compatible with the iPhone. Technically, ATT is authorized to place the proper data plan on your line at any time because it is written in the terms and conditions as a requirement with any smartphone, whether it be a BlackBerry (NSDQ: RIMM) or the iPhone.