Overcharged

Cell c Debited more money In my account.when i was calling customer service the consultant told me about pro rata fee and charges .and they told me that i reversed a debit order in December.im surprised because i paid cell c earlier in the December.i want to know why am i charged this much .cell c need to train they staff not sell false adverti*****t.why was not informed about those fees charged before joining the contract.kindly refund my money as i need to pay medical bills.