The rule that I have always been told is that if it is based upon your wireless web traffic, it is considered data minutes. So for most, it is unlimited.
If you use your phone number for any type of features, text messaging or sms (whatever it's exactly called), then you will be billed for that.
Long story short, you can use Agile without worry. Well at least I did on my sprint vision. On a side note, I tried Agile and did not care for it. Get a program that will run in the background.
If you search the site, you will find some great info written by some of the members here. Everyone here is great to get advice from. You will want to keep visiting so that someday you will be able to help others. It is addicting.
Also, welcome to the boards. (I am a veteran yet to be able to do that

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