Burger King review: drive thru / night manager

Drive thru refused to accept coupon because last digit was left off then told me to wait for 10 min while there was a line of cars behind me. Then came back to tell me again she would be unable to process the coupon because I did not know the last digit. Called later on to complain and the individual who answered told me she was the person at the drive thru and the manager. She then told me there was too much static on her end and would be unable to assist me.

How hard is it for someone to process a coupon? Even if the last digit is REQUIRED, you would think they would have a copy of the monthly mailed out coupons or at least have the ability to guess numbers 1-9...