my aim on my sidekick still works with out minutes?

[Undes01]

so I'm on prepaid on my sidekick, when i use to run out of minutes i would lose aim and internet too...now when i run out of minutes my aim and internet still works?...is this something new with tmobile or some sort of glitch?....please no one comment this just to tell me that sidekicks suck or that tmobile sucks...I didnt post this question to get a bunch of lectures of what phone service is better...just looking for a simple answer if anybody knows. please and thanks