Mr Delivery must keep their coupons!

I ordered dinner through the app while in Nelspruit When I received the delivery I asked the driver whether my coldrink was with. He said yes but I was soon to discover that it was not the case at all. I raised the issue, now Mr Delivery will not refund me, I was given a coupon instead?? I paid for everything I am not interested in a stupid coupon Refund me!