Incorrectly billed and not refunded

End of last month my credit card took its payment off from my cheque account as it should then took it of a second time there was not enough to in for the second time so a was billed a R100 for it I phoned them and they said there were problems like that and they would refund me the R100 it's been a month now no refund or reply. I even sent a complaint though there website and still nothing. I'm very upset about this I thought I choose a good bank to be with.