Disgusting Service

I settled my Loan account with FNB on 24 November 2017. I got my settlement amount through FNB Online banking. My debit date is the 27th of every month. FNB decided to debit my account on 27 November 2017. I sent them an E-mail on 30 November 2017 regarding this deduction because I really thought it was an error that they could rectify by reversing all the fees charged after the account has been settled. After several E-mails FNB decided to refund me R436 which raised a concern from my side because I was charged interest on 25 November 2017 , and all the charges included on the normal installment that is admin fee & Credit Life, after the account has been settled. On the 12th of December 2017 I called FNB to get clarity on the matter and spoke to the lady by the name of Zinhle for 23 minutes without getting any clarity. Zinhle told me that it does not reflect from their side that I did log to my FNB online banking which raised a question from my side on how did I manage to do the transfer to my loan account if I did not login to my online banking. She also told me that I short settled the account by R426 of which that amount reflects as amount in Credit on the statement. Zinhle sent me an E-mail saying she has escalated my query to their Admin Department however I have not received any acknowledgement E-mail / phone call from FNB Admin Department. Why would such a big bank ***** from loyal customers?