They call and don't leave a message. I have no clue who they are.

I just received a phone call as well.. I didnt answer not knowing the number.. They didn't leave a message

I had a call with no message, I called the number back to see who it was. A man answered saying he was from the Kirby corporation and asked if I was Mary. I said no thinking it was maybe a wrong number. The guy then proceeded to try to give me some sales pitch about how they will clean my carpet for free and asked when I could set up an appointment (even though I wasn't Mary). I said no thank you and asked politely to be removed from this call list (they have called many times from many different numbers). The guy then instantly hung up on me. What a jerk! Don't fall for this scam!

They are calling from Kirby and received your number from a 'friend'.  One of your friends/relatives/etc referred you and gave them your number.  They will clean your carpet for free and will give you a sales pitch to buy a Kirby.  No obligation if you can keep a firm no :)