Doesn't refund you when items where paid but not supp****

Placed an order with a franchise via MR D. I paid in R9 x6 for milkshakes. I received the fountain soda that comes STD with the meal. Zero refund given to me. I have emailed them countless times I get a R15 voucher on delivery and no comments on my actual refund. I went to the store itself to ask for my refund. They said they only bill Mr D for what was given and my money is not with them. They also said they have asked Mr D countless times to remove the shakes from their menu as that branch doesn't even have a milkshake machine. Yet MR D tells me they want more proof (pics of the whole meal received) and not just the one pic I took of the fountain soda. Their app by the way says photos optional when I wrote my initial complaint. Point of the matter the store doesn't even supply milkshakes is that not proof enough that I didn't get milkshakes that I paid extra for ?!?!