iPhones & iPods: iPhone - Passive downloading?

iPhone - Passive downloading?

I have an original iPhone. It works great. It is unlocked and has an AT&T pay as you go sim in it.
Today, I started receiving messages that 25 cents or 28 cents was being deducted from my account.
I had made no calls nor sent any text messages. Then tonight, while in it's dock and connected to the Macbook, my account was wiped out. I checked my AT&T account and it stated the transaction was a "GPRS" type as had the earlier ones been.

I phoned them and was told "oh, those iphones download constantly". This has never happened. This kind of passive downloading. Anyone know what this is about? Will I be wiped out of any money I put in????