I heard through some individuals with other smart phones that if you tether through blue tooth and not through a cable or hotspot wifi you can get internet without the carrier noticing the tethering option being used. I could be wrong...
Official tethering: sets up a hot spot allowing 5 computers to connect, costs $20/month for 2 gigs of data.
Nonroot tether: Allows you to tether using a USB cable or bluetooth. Usually have to pay for the app but it piggy backs on your existing data plan. No monthly fees.
Root tether: Sets up wifi hotspot, totally free, as many people that want can connect to your phone and get internet.
First 2 options are 100% possible. the 3rd option will depend on if we get root or not.