No, we are not allowed to do that! It would void your warranty and we can't do any work that can't be warrantied by Lowe's and Ultimate Home Services. Carpet manufacturers insist on new pad under new carpet for any type of warranty.
You are required to purchase new pad from Lowe's and you'll be glad you did. Lowe's offers a wide variety of padding from the basic "Super6" pad to the ultra soft "Stainmaster Elite Foam" pad and everything in between. New pad is nice to walk on, clean, free of residual odors, and increases the life of your new carpet.