I had a similar problem with a two servo elevator in a katana. The two ways i can help you with are 1 buy aservo reverser 2 open the servo base and reverse the motor wires and swap the two outer wires on the potentiometer or where the wires mount on the pc board or cut wires and join and insulate them. Proper soldering is important and both, motor and pot, must be done not one or the other because servo will fight itself.
David