Extremely poor customer service

I don't even use Worldpay. I tried to contact them because I was getting post from them for a previous occupier at my house. I kept forwarding the post to them saying he no longer lived there and nothing happened. Finally I called them and asked them to stop sending me post. They said the letters would keep coming to me and insisted they could not contact the previous occupier because of 'privacy'. I work in the area of data protection and know this to be a nonsense. There is nothing in the Data Protection Act to stop a company contacting its own customers. When I asked to speak to the person's manager they said I couldn't. I was so angry I hung up on them, something I never do to anyone. I tracked the previous occupier down on Google and he said he had tried to unsuccessfully cancel his contract with them. It appears it is not in Worldpay's interests to get people's correct addresses, because they can keep charging them money even when they have cancelled their contract and hope they don't notice.