Stop spam calls

I receive a call from this same XXXXX male a few times a day despite, Now, Hanging up each time I see it in the caller ID. He doesn't even give an opportunity to say hello! Started speaking as soon as I answered. Claims to have evidence of my paying too much for my gas and electricity 'supplier'. In actual fact, I am not connected up for gas and my electricity is fully inclusive in the small rent I pay to my landlord, The University of Manchester, Who are MORE than fair when looking after our