XXXX Group XXXXXXXXThey started calling me a couple of years ago claim that I owe them money but refuse to send me proof. Keep asking for my personal info so they can verify who I am. Told them if they wanted to verify who I was to send anything they had to say to me plus proof of claim/debt to me in the mail and if I got it and it was mine I would verify. They refuse. 
Some of the original calls said they were calling about an investment issue. I do n't have investments so I hung up on them. 
Still call constantly, blocked numbers, unknown names, cell phones. I have blocked them on all my phones. I think they are just a big bunch of scam artists.