I don't personally use the service but I would guess that using AIM does use your prepaid balance whether or not you make calls.
Hi everyone I just got a new T-Mobile to go phone (Motorola v300) and it comes with 60 minutes of starter time. For some reason these minutes are being gradually used up even though I havn't made any calls yet. Does t-mobile charge minutes for signing on to AIM or checking account info on tzones? Also, where on the phone does the headset plug into? Thanks in advance.

Chowhound
Comic Vine
GameFAQs
GameSpot
Giant Bomb
TechRepublic