internet sharing

[lfrp]

hi, I just have a quick question, i installed a couple of weeks ago the mr5 and is working really good so far, if i get tired of it someday ill try the new silence mighty mike....
there is the program called internet sharing, so i connected my laptop through the usb to my phone and i was able to browse the internet, however do i get charge for it? for using my phone as modem? i have unlimited messaging and internet on my phone but not sure if it covers that.... i just dont want to keep using it everywhere and then get hundreds of dollars charged from sprint...
thanks.....