******* who jus stole my vouchers

on the 31 December I redeemed WI vouchers and it went through at the Lambton store, minutes later they tell me it declined. we argued for about an hour and it was the cashier, supervisor and manager. the manager said it didn't work but initially they told me I only needed to pay a difference, when I took the difference out in cash , that's when they said the vouchers declined. Since I have also spoken to head office and they said the matter will be resolved as at the end I had to pay for the whole meal. Nevertheless even head office cannot resolve a small issue as the staff did ***** my vouchers, the manager even called and said he will get back to me but nutting since. Will anything be done about this as im sure it happens a lot.