Unsatisfied customer

Today i went to redeem my birthday voucher, which was offered by u guys. The total amount came they tried to redeem, i was left with a balance of R3,75. All the waiters came nobody could fix the issue. Instead of subtracting the amount for the cake, they told me to pay the whole amount due... I was very unhappy about that.... Mug an bean offers customers an do not know how to satisfy, with the prices being sky high as well. They have lost points with me.. Thanks