Gym double debits 2 months in a row and tells me he will keep it as a credit?

After my email to the gym to cancel as its affected my credit score Joe called me to tell me to reverse the 1 x R399 as well as he will be keeping the R399 that was debited in April as a credit, so 2 debits in March and 2 in April and he wants to keep my money.

when I asked if he would allow his money to be taken and not returned and kept as a credit he said yes he would ?

how many peoples account have been double debited and we have no idea until its happened twice on our account and still to be told oh it was a mistake.

yet I'm the one paying for the gyms mistakes?