Shirking responsibilty

I ordered from Nandos using the app, I had a R30 voucher which i app****. When i wanted to pay using my card it gave me an error message.I tried 3 times and then decided to just swipe my card. I kept on applying the voucher and it deducted. However when the delivery guy arrived the total was without the R30 deduction, so i queried it and was told tht he is only the delivery guy I must take it up with Nandos. I then called the Customer Service Dept and was told that if there is an error message then the voucher doesnt take and that i have to re-activate. Really? This after it asked me to insert the voucher and deducted. No one wants to take responsibility, the delivery guy is saying take it up with Nandos, Nandos is saying take it up with clientele. Very sad