Stop rotation on collision

Ive got a ball that has torque applied to it to make it spin, i want it to completely stop rotating when it hits a wall so i can add a different torque to it, but i can't do it.. but i want the velocity to remain! now due to the type of game I've got physics material on the ball and walls which make it frictionless and because the velocity needs to remain changing the drag/angular drag isn't an option also freeze rotation isn't an option because i need to apply a new torque to it!!

any help would be greatly appreciated :)