BILLED FOR YEARS FOR NON EXISTENT CONTRACT/SERVICE

I am a 82 yr old pensioner, for years I have been billed now R115 per month for a contract I did not sign up for and despite reporting it previously, the billing keeps on coming. If I don't pay it then my service on my normal monthly contract gets affected and I get disconnected. I was told that I can only cancel the service once the arears is paid, but I have been paying for years for a service I am not even making use of or signed up for. I am happy to pay for my normal monthly contract which I have been doing all along but why should I pay for a service that I am not using or signed up for. Not to mention the amounts that I have already paid towards this non existent service. I hope Vodacom will contact me with rectifying action, but I will not hold my breath over it. If Vodacom see their customers as more than just numbers, then they will do the right thing.