Receiving mail & phone calls at a family members adress?

Okay so a couple months ago someone called my cousins home asking them if I could use them as a reference. When my cousin asked what for, they said it was a personal matter and that they weren't authorized to tell him. He said sure and gave his full name. But that was it, no address nor any other personal info.

He didn't tell me about it. This week he received junk mail in my name at his home. He called me and asked me about the reference info and why I gave his address. I told him that I didn't even know his address to begin with nor had I applied for anything that needed a reference. Even at that he and I hardly speak unless party invitations or family get together' s. We have each others numbers for those purposes also.

My question is; how do these fraud companies even get all this info and who do I report it to?