Mr price mobile contract fail

I recently agreed to a Mr p mobile contract over the phone and I am really regretting it. What they don't tell you is that once your contract data is finished you cannot buy any from the stores, the only way to get is if you do a debit order on your bank account. I thought I was on a fixed R129, per month but now I find out they put me down for a bill limit of more than that, so I end up paying more at the end of the month. Its ridiculous that you don't get asked what you want to spend each month and even more ridiculous that I can't get data without signing up for a debit order. I'm now stuck in a contract that wasn't fully explained to me, so just be aware before you take on this mobile company