Definitely a scam. Don't answer their calls and tell them to remove your number from their list. The guy never knows what he's talking about and sounds like he's reading off a script.
I asked them to not call me again and his response was that I needed to change my number because he was going to continue to call and he was going to share my number.
I got the same! He said he would not stop and would call as often as possible. I've been receiving calls from eight numbers ever since- I've blocked every one. Why call if you are selling or collecting debt?