MFC leave me alone

Worst company EVER!!!!! I am being HARRASSED for a payment they acknowledged receipt of and send threatening letters to me. It's disgusting how they treat their customers and I had to deal with a "MISTAKE" they called it that THEY MADE on my account for a YEAR. Promised its sorted. Um.... how are you going to sort out now that you reported me in the past and handed over my account for YOUR MISTAKE?????? They have royally *****ed me over and my credit rating and I don't even get an apology and now I'm being harrassed again. MFC LEAVE ME ALONE PLEASE