Blackhorse loan

First time on here so here goes
I took out a loan in 2007 and did default, contacted black horse who was happy to help until I had a letter from a debt company, to try and keep this short the original loan was for 3000, I continued to pay collection agencies without defaults but they kept getting sold on and the balance was not coming down, after a few years I put it to 5 per month as I did take the attitude if between 60-100 wasn’t changing anything I may as well pay 5 pm.
A few days ago I received a letter from Black horse stating they were going to send a cheque of 47 and to cash it ASAP, I have contacted them today and took it to complaints who phoned me a few hours later, I explained I felt I was unfairly treated through the whole process which went on for a couple of years, they disagreed and said the cheque was because they over charged me interest and a little bit extra, reluctantly he has sent it now to complaints but said it wont take long as mine is a very straight forward no, in his manner I think they have already made up there mind, I have asked for a copy of T&C
I was on a 0hr contract at the time of taking out the loan