Unfair treatment

I get to Burger king in Revonia Sandton, and i asked toe bê given an opportunity toe download the app so that my order amounts to the coupon voucher i get from clientele, Then i was told i forfeit my vouchers because they only take one but when i asked to use the other voucher they say i cant take it, i was bul**** by the manager made me wait for more than an hour without any assistance telling me there's no thing they can do