rpm idles way to high cause the jeep to accelerate quickly

I have mentioned this problem several times after purchase and it continues to go unfixed I am Pissed off about it, if I take my feet off of the brake it takes out by itself and can run 10-20 mph without my feet on the gas pedal, it also shifts hard in the first to gears. the mechanic checked it out and said it shouldn't be doing this and stated when he gave me the jeep back that it was fixed and it hadn't been fixed at all. I am not happy with this dealership.