False credit report update

I took a credit card with nedbank didn't use until months after for a major purchase that needed a substantial amount that resulted in maximum using of My credit available I then paid it back in 25days but my credit score has dropped I can't get any credit because I'm in arrears of which thats not true I paid the money back in days, I reported this soo many times but it has not been rectified I'm writing emails everyday but I'm failing my life is in a stand still, I am considering leaving this bank