Charged twice and they wont refund me!

I use Mr. D all the time. I've spent thousands of rands on the app. My wife even more so. Today I ordered lunch, the app bombed out when I was paying, so I tried again and it worked. The driver comes with my delivery, and then 2 minutes later a second order arrives. I told the driver that I already received the delivery and he said there is nothing her can do I must take the delivery. I then immediately call the restaurant to ask them if I can return the food. they tell me no i must tell Mr. D about the problem so I send them a mail. I then get a reply with them telling me I should not have accepted the delivery from the driver. now I sit with food I did not order and paid twice. will never use the app again!