FNB refuses to fix an error and ******* set off on a customer's account

FNB admitted to an error on their part regarding a payment allocated I correctly on a credit card. Now they have triple debited the account and blocked it, taking R9000 without informing anyone or giving any feedback. They refuse to fix it, meaning the client is without medical aid and other account not being paid because of their mistakes and complete unwillingness to fix what is their error! The set off is ******* and wrong and how dare any business function that way. It is the most ridiculous thing I have ever heard. What is the point of being a premier member when they refuse to give you any kind of assistance