Bad experience

<p>I had a loan that I settled on 22August2016 after receiveing a settlement quotation, but since September have being receiving statements that i still owe them.Every month I contacted them and they told me to ignore the statements since my account is settled. I even received a settlement letter to confirm that.On the 7th January 2017 I received a message advicing me that my account is overdue and is going to be handed over.I contacted them again and they still reassured me that everything is ok.Today I received a call from the collection company advising me about the handing over and that I have been blacklisted, when I call them today they are telling me that there is a balance on my account that they are going to write off today.Did I make a mistake by paying up my loan before time?Is it my fault that I got an incorrect settlement amount?When I contact them why wasn't I advise in one of the many calls I made to them?</p> <p> </p>