Being Charged for items I did not receive

I got charged R600 for data I didn't receive. Despite attempting to resolve the issue since the 11th of Feb 2016, it was still taken off my account at the end of Feb 2016. I then reversed the debit order, and told them that the normal subscription amount would be available in my account once the matter had been resolved. They processed it AGAIN. I don't want to pay R600 for 3GB of data as it is a big *******! But to pay it and not receive anything is unacceptable.