Just don't answer it.

Spam caller

I called it back it was obvious it was a robo-caller of some kind, but it did give me the option of being put on a do not call list, but this might have been a trick, since I am already on the national do-not-call list. Tele-marketers should be hunted down and imprisoned. A use for Guantanamo Bay that we could all support...spammers too and those guys that caused the fiscal collapse and my mail carrier and...

No one was on the line when my son pick up the phone.  Caller id said GB Marking Co

Called but left no message. I don't return those calls so I don't know who it was/what it was for. Called from Greenwood, IN.