Refuse to refund the loyal customer

I had a bad experience with FNB call center agent and his supervisor who are ***********. The reason i phoned the call center is for me to be refunded an amount of R365 that the bank owe me, so the call center agent and his supervisor went into my account and told me the amount have been paid they pick up transaction amount which i made of R355 to someone and told me it was paid by them (FNB) they did not ever check properly, it was like im crazy to them.