WMWifiRouter and sprint questions

[JustusIV]

Hello, i purchased my phone about a year and a half ago and the sales rep specifically used that i could hook it to a computer for internet access for no additional charge as a selling point of the phone. Before i knew what i was doing it was a pain to get it working but i did. 1 year later i walk into the store and i was told that to do it would be an additional 40 dollar charge a month for doing that, I didnt give them my name or number and just turned around and walked out. I fell scammed by this and additionally when i talked to another rep about this she was like i promise you the sales rep never said that. And my only response was i promise you, you weren't there and you have no clue how the sales rep sold me this thing so don't promise me something you have no clue on. Anyways long story short i heard there are some tweaks make it more hard to have sprint detect you are using something like WMWifiRouter, is this true? Also since my plan is "unlimited data" how much should i stay under. I mean i used to stream music to my phone from my PC all the time. I have no clue how much i used and don't care. But if i am trying to be cautious what should i stay under. God i hate living my life in fear especially on there sales rep misleading information. Any info is appreciated.
Thanks
JustusIV