Very disappointed........

After I saw that Vodacom deducted R520 instead of R350 for April I immediately called them on the 3rd as the debit order only went off on the 3rd because of Public Holidays. I've cancelled the Extra R170. Now on the 9th I receive my Bill for May - the R170 data was not cancelled. The Billed on 1st and although I've explained that I already called on 3rd to cancel they don't want to refund me??????