Closed account but still receiving interest charges

I am extremely irritated right now, I settled my Hub account and requested that they close it almost two months ago and I have been sent a closed account letter now they show on Experian that I still owe them money. Despite me asking that they update their information it now becomes my problem. I am tired of the level of incompetence received from this company in requesting them to attend a simple task. I want the interest that they have charged me reversed and I want this rectified, I am busy working and do not have time to contact them all the the time for something which I have done already so many times