DSTV Unauthorised debit order amount

I am on a price lock package and this is now the second month in a row that you have taken a higher debit order than the agreed amount. Last month I queried this and requested a refund. I was advised it would take two weeks. To date, no refund. This is absolutely ridiculous. I even asked if this would happen again and the person said he cannot guarantee that it won’t happen again. This is theft. I cannot believe that this is the way you treat your clients.