Incompetence

From October 2015 I have advised FNB that ,my paydate has changed and therefore I need the payment date of credit card to change accordingly. To date, this has not been resolved. Instead I get charged bank charges due to their incompetence and makes my credit record reflect bad. Eventually when someone does decide to change the date, FNB debits my account for R4500 which is the payment due and then the next day for R2700. Not sure why. They still then send me an sms saying my account is in arrears. How the hell is it in arrears if I paid more than what is due??? Why must I pay 2 installments just for a date change by a few days?????? Why must I get charged bank charges for return debit orders if they dont get it right and they debit my account for more.