Bad Treatment by FNB

FNB treated me badly as a loyal customer. They took an amount of R5315.12 from my account without my consent in 2020. The bank was supposed to write off the interest of R12448,99 on my inactive cheque account and upon realizing that I had money in the account they decided to take it and later claimed that they used it to settle the interest. The interest was supposed to be written off not partially because there was money in the account. My attempts to resolve this matter amicably and have the money returned to my account is falling on deaf ears. A year later, I still dont have my money. I made several calls, sent several emails, have been pushed from pillar to post