Unduly Handed over for Final Bill

I requested in November for my account to be closed end of December as I was moving, I never received any feedback regarding the closure. I had to phone Impact meters numerous times and even went to the premises to confirm. Then I returned in January to the premises of impact meters to settle my account in full, but they turned me away and said my final bill was not yet processed. I then proceeded to wait for the final bill but it never came! Then they handed me over to attorneys for non payment! When I confronted Impact meters they could not prove that the Final Invoice was sent to me and therefore sent me the invoice which I paid immediately in full.But now they want me to pay the lawyers fees which I am not entitled to pay as the fault lies with Impact Meters. This is totally unacceptable