Never settle an account that was handed over!

A few years ago I lost my job and couldn't afford to pay my Truworths account. My account was the handed over to a certain firm of attorneys which I fully understood. I was never contacted by anyone for the settling of my account. I however was the one who called Truworths to ask for my balance to make arrangments for the account to be settled. They gave me the contact details of the debt collectors. I called them and made the arrangments. I paid my full balance of Truworths in a two part payment that was deducted via debit order from my bank account. This was in March 2017. Up until today Truworths still have the full balance that I had and regularly sends me sms'es offering me a discount on my balance... If my account was settled, what balance do I still have? Everytime I speak to someone over the phone about this they always tell me the same thing... "we will escelate your query to the relevent department and they will be in contact soon"... I'm still waiting. It's almost a year...