FNB loan gaining interest after its paid up!!! Irritated by their lack of customer service!!

Irritated by their lack of service. About a month ago, I paid up my loan account and I called FNB for them to check if all is in order, the lady I spoke to said all was paid up and that I should call after 7 business days to receive my paid up letter. after 9 business days I called them only to discover that the loan had gained interest and it was not closed yet. I demanded to speak to a manager but they deflected my request saying they will escalate, after that a few days later another lady called me saying they have resolved my query and that FNB will close my loan account and pay the interest gained. this was beginning or mid November. since then I have called several times and each time I am told that they will escalate and that a supervisor will call me back, guys it is 08 December now, my life has stopped and I am flagged at the bureaus based on an account which FNB is not resolving and delaying me to move on with my financial commitments. I spoke to a lady trying to assist me who escalated this and gave me a ***. but still nothing has come out of it. I was supposed to be called back by a manager called Jabulani Sikhosana, still today I wait. FNB needs to reimburse my airtime that I called and the damages I inquired from not being able to meet my financial objectives.