Charged for Data use while tethering on Sprint ?

[morganpe]

I have tried to sift through the forums but haven't really seen a specific answer to my question.

I know that you can teather the 6700 and I have done this without a problem. I have the simple Unlimited Power Vision Plan - No specific Data plan. I have not teathered tons and have not seen any change on my bill.
Has any one been caught by sprint using the ppc 6700 to teather on a non data / teather plan?

Any billing issues etc.
My brother in law needs to be able to teather regullarly for laptop internet access but doesn't want to pay too much &/or get a huge fine / bill for using the phones features.

Thanks in advance - I love this site it has allowed me to get the most from my phone and make me the "genius" at work.