Who called from 3129247977

They are checking to see if you answer your phone.  Once you do they sell your number to marketers.  I never answer if I don't know the number because if they are real they will leave a message

Called my cell; no name, no message.

Called to tell me I had been selected for a free cruise line vacation; but needed to press 2 to be connected. Did not do it of course.  Hung up

Just now called my mobile phone. The number wasn't attached to any number in the "phone book" in my phone so I hit "ignore".

Called my cell phone, no message left.