Ok this is a fairly easy problem to fix, if whats going on is the usual problem.

You need to flip the throttle channel reversing switch on your radio, then hook up the motor wires to the correct wires from the esc (just connect them to the opposite colour wires that they are attached to now). Now reset the speed control for the new setup.

Let me know if it works, its tricky to get your head around and I may have explained it poorly.