Have you tried that on a Halfords Carerra with SR kit?You can adjust the speed of just about every ebike ever made. I bet even yours can be adjusted by the settings if you know how. Tell us what you have, and I'll tell you if it's possible.
BTW, Bafang can factory lock all their LCDs on request making it impossible to change the speed limit on any of their kits. I can't unlock them myself.