Sprint Wireless Internet

I have never had to watch how much I used to the internet. Who does that? That's very absurd to me. I've been paying overage since the summer of "09 cause I was never told that I would have to check and monitor my overage. I want out and as soon as possible. Also, I was promised a $150.00 rebate and they told me it was a mistake and I only got $50.00 and that payment came 2 months late.