I got the same issues with Nextel, I think they just upgraded me to sprint.
The $10 plan read off a paper something like:
Access to over 80 popular websites, other sites and downloads may cost extra.
I said what does that mean? how do I know I'm not got to run my bill up to $400 again?
She read the paper again. I went with the $15 unlimited data plan with a month free trial.
If I dont like it I'll drop it. (They waived the $400)
This is my data plan
Nextel | Data Service Pack