Gym machine error costing my account.

I missed my gym payment for November and now they told me that l have to pay R339 so l could continue. I swiped my card for payment and the machine took R813.86. When l saw the a bank notification that they overcharged l asked them why they took so much and they said it's machine error so l should bring my bank statement for them to verify the transaction and refund my balance. I provided the bank statement and they started telling me that they will not pay me back because they dont have it and that l should try with my bank. My bank says they have it and should refund me. My installment is R300 a month and l did not have any problem paying the R339 for missing a payment but l am frustrated for them to take so much when l owe less. Now l am using my own resources calling bank, calling the gym, trying to get my balance back. Why should it be my problem, why should their machine error affect me, why should l suffer for that?. Please help me get my balance. If l deal with this issue my way it will not end well. Please assist me. This happened at planet fitness pietermaritzburg, Liberty mall on the 2nd of December. My number is ***. I can't take that, their error their problem... I am frustrated.