A deal that doesn’t give you anything!!

Bought a 5 free smoothie deal with plastic cup. Have not been able to use one of them - they have told me that my voucher is not valid! Funny that it came off my credit card!! On Wednesday they told me they would contact head office .... still no response so have phoned again and I got the same response that they would contact head office on Monday. Very disappointed. Won’t be going for any of these deals again.