Who called from 6121892472

This number is calling me every day and not leaving a message.  I call back and it's not a valid number.

same here. Called this morning, when I answered a machine voice says "Goodbye" and disconnects

called the number back and not a valid number

Got call called back and  got message disconnected charged or on longer in service

I answer and a automated voice say "goodbye." I'm worried it could be a hack or something of the like

This number keep calling me then when I answer, it says goodbye.