Harassment!!!

I have been paying my Mr Price account diligently for the past 2years. So well infact that I had a phone call thanking me for this. BUT, once I decided to settle the account, all the problems came up. Aside from the incredible effort it took to get banking details from them, my major headache has been the harassment. This past weekend was the worst of it. After transferring the money I still keep getting phone calls threatening me if I don't pay? I have paid, but, no one cares. I would like to know why I should not close my account right now?