Disputing unknown charges on the account

I opened a bank account at FNB last year and the consultant suggested an Aspire Fusion account which was R115 per month at that time. The consultant advised me that I’d get a R500 voucher to spend at Checkers after 3 months of getting my salary transferred to my FNB account. I requested to change banks at work and use my FNB account. After 3 months I did not receive any voucher from FNB. I continued buying using my FNB account so that I could earn eBucks, and I was not earning them yet I am buying from their partners such as Clicks. What stood out for me was when I purchased from Clicks online and I was supposed to earn 699 eBucks from my purchase and I never received them. I reached out to FNB and was advised that the eBucks should be available in my account after 30 days of purchase. I never received them at all.

The consultant never told me about an overdraft on my account. I got tired of **** promises from FNB and switched to Discovery Bank which is so good. I changed banks so that I could get paid from my Discovery Bank account. One day I log in on my app and I have a negative balance of R1538. I find it unfair that I have to pay service charges whilst I haven’t been using that account for months, and also I don’t understand why I have unknown charges on my account. I would like to have the account closed as I don’t want anything to do with FNB. The live agent I spoke to is refusing to close my account due to a negative balance on it and I refuse to pay for charges that I don’t know about.