[Landlord UK] Energy bills for multiple properties being sent to my address

Hi! I’m a first time live-in landlord (close friend lives with me) in South Wales - purchased 3 years ago. Since owning the house I have received a several SSE Energy bills for multiple properties in Cornwall, all addressed to different people. The previous owners of this property were estate agents in Cornwall so I assumed they had forgotten to change their correspondence address. More bills for new names keep coming through regardless of the fact I’ve contacted SSE multiple times to clarify that none of these people are known at this address. Any ideas?