Debt collectors still calling me yet issue was resolved

Not long ago I posted on Hello Peter about Netstar continually sending me emails of non payment yet I had cancelled my contract. The error was that that when I cancelled someone from their side did not update that I had cancelled. Previously someone from Netstar called me advised that the matter was resolved and amount outstanding cleared but for a few times now I am receiving calls from debt collectors threatening me with black listing. Today I actually received a very uncomfortable call from a debt collector who I tried to explain that the matter was set aside but she turned out to be very aggressive. Please communicate with the debt collectors to which you handed me over so that they stop calling me