FNB service sacks

I recently paid up my FNB loan in December 2018. I forwarded the proof of payment for on 24 December 2018 of the final amount . I then made a follow up the first week of January 2019 to check if all is in order and the agent I was talking to informed me that they did receive the payment, he then asked me if I am aware that I have over-paid my loan account, which I answered that I was not aware of such. The agent advices me to forward an email to FRB requesting that they should refund me the credit amount and I should attached the necessary document ( proof of bank details and also ID copy), which I did on 07 January 2019, which FRB rep**** saying that they acknowledge receipt of my request. I have been making follow ups every weeks ever since and till today my request hasn't be resolved. The last reference number I received is 23004. To think that I haven't missed a single payment during the duration of the loan and this i what I get as a customer who has paid up his account and FNB acts as if I still owe them but it's them who owes me. I don't see myself taking up any loan or credit card with FNB in the future, their service is worse and their agents keeps giving me sotires everytime I make a follow up. This is ridiculous to say the least.