Money gone

I've ordered on Monday 10 June on their app a pizza I've added a voucher that i got from my bank, the app just said order timeout so i tried again for the second time and my voucher didn't wanted to work said that i just used it but the order didn't go through. I phoned the store and they said i will get my voucher back but its been 4 days and the voucher still don't want to work they took that money and i didn't get anything the guy that i spoke to again said that its gone. This is unfair this is so not right. The guy said there is nothing that he can do. Their app is just sh**. This is Debonairs Tygervalley Western Cape