schocking service from FNB RE blocked cheque account

THREE Transactions of R2500 *****ulently went through my credit card three months ago and have not been credited by fnb in spite of notifying the bank. when querying this , the bank blocked my check account & now I cannot do any transactions . when trying to get hold of fnb they are overloaded with calls and cannot assist so I am not able to do any transactions! getting hold of any private banker is impossible