Bad Attitude at the Core

Haloweb have been billing me for a hosting account on a domain that is not even on their system as I have had it parked with WebAfrica for 4 years now. I simply used them to register the domain and then I transferred it. When I received an invoice for this around 2 years ago, I immediately spoke to their Accounts department - who just gave me attitude saying I should have cancelled. My response was that I never signed up for a hosting account with them, so there was nothing to cancel. Eventually I got hold of the owner, who said he would come back to me. He never did, but continues to bill me every month. I have tried on 9 or 10 occasions to get this sorted out, but no-one seems interested.