Harassment/ *******a

This company is Harrassing me and I have had enough of it. They call on a number which I block and then they call on another number. When I try call back call not answered. This company seems like ****ers to me. They say I owe South African Blood Services money. They don't have details at all and if it was a hospital account I would of received an account from hospital. I have never received blood. These calls need to stop immediately