Battling to get through for a refund

I tried to book an extra bag in at checkin at a cost of R250.00 – the attendand advised the payment was declined though it showed Pending on my side and she said she would cancel the transaction. Well today the payment goes off on my account, how do I go about receiving a Discount as I never managed to book the extra bag in – cannot get through to the email provided on their chat *** is not valid.