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 $$anonymous$$ts 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 w$$anonymous$$ch 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 :)