Bad Credit rating

I have use FNB bank to get revolving loans from time to time and always pay them back promptly. I closed my credit card almost 2 years ago and after getting my credit report I realised FNB never closed any of my accounts and that is giving my report a bad score. The only open accounts (which has zero balances) are all from FNB!!!! They are a financial institution and they don't even help with the credit scores by just doing what they are supposed to, CLOSE THE ACCOUNTS on the CREDIT SITE!!!!!! I hope this can be sorted out promptly!