FNB ruining my credit profile

I paid and closed a credit card with FNB. this account is still sitting on my credit profile. I wanted a paid up letter but no one in the collections call centre can help me. They transfer me to the cutomer help centre who transfers me back to the collections. I am going around in circles. The account is closed, but is blocking my ability to apply for a homeloan. I'm at wits end. No one in FNB wants to help