Calls cell phone 5 times a day. I don't answer.

This number has been calling my cell phone and when I answer no one is on the line.  I have called the number back and no one will answer will I call.

these people have called me over 30 times in the past few days, I have only answered like twice and both times all that I could hear was static. I hung up both times and have refused to answer this number anymore.