Does your phone (what kind?) have a mobile Hotspot option installed as provided by your 3G service?
Is it up and running with a name & password? You can find out by looking in Settings>General>Network>Personal Hotspot, that's where mine is seen.
If it does, and it's working correctly it should show on your iPads Settings>Wi-Fi>choose a Network.
Just tap the Hotspot, enter the password and you should have wireless service on the iPad.
My Sprint iPhone 4 w/optional mobile Hotspot works just that way, no problems.