Netstar - Invoicing for services not rendered

I am so frustrated with Netstar. Despite correspondences going back to 2017 and personal calls - this company handed me over to Nu-Debt in 2018 and again now to Creditworx - despite me not owing them a cent. I bought my car second hand - and have drawn their attention to the fact that I have not got any active service from them. I even ended up paying R513 just to get NUBEDT off my back. Yet they persist in trying to invoice me for further amounts. I have made every attempt - including efforts to speak to their MD: Pierre Bruwer - yet am unable to get NETSTAR to rectify their mistake and subject to continued harassment from debt collectors. I am about to get legal advise on the following: Surely it is ******** to bill for a service you have not implemented? Surely I have recourse for damages? I am disgusted to say the least.