After another think, It might be done with a couple of wires at the controller. Open the black box on the seat tube and see if there are two single wires either joined by a connector to make a loop or not joined, or their might be a loop of wire that comes out and goes back in. The colour will be most likely white or grey. If they're not joined, connect them and if their connected, disconnect them to reverse the function.
Here's the manual, which shows how to delimit the global speed. From memory, the code is 0512. It might be that there's a setting under Hnd (page 25) because there are different software versions, but I'm leaning more to the wires as the solution.
That bike is a fantastic base to make something decent out of. A KT 15A controller and a 48v Dolphin battery will transform it into a really nice bike when the original battery packs up. I made a sample like that for Kudos, but it got severely damaged in transit, so they never got to try it. I tried it before shipping, and it was fantastic.