Appaulling violation on my rights

I have recently had the most horrific experience with standard bank. A few years ago I had lost my job and was unable to pay my credit card. I then had a low income job and started paying again, after which I paid up the account and requested it to be closed with my 1st bonus in 2017. I app**** for a job this year and was rejected due to the fact that the account was in arrears on this credit card I had paid up 12 months ago. Coincidently the job was with standard bank. I had then contacted standard bank requesting that this be corrected and has not received any satisfaction they needed me to send them confirmation of paying the account. I was then told they will rectify my credit profile in 14 days it has long passed 20 days and I have not received any feedback.