Dstv charging for a service that I terminated a while back

Dstv says I owe them whereas their services have been disconnected over 2 months now, 2 months later I am told i owe R500. Like what is going on, i am on the line with one of the agents and she doesn't have the answers... Telling my about a decoder that I stopped using a while back, How can one deactivate a "service" and keep something else on, As a customer deactivation / termination of service should be for everything and not keep anything hanging, I am done with dstv.