Keeps calling, don't answer, no message left

This number called my cell, I did not answer. No voice message was left. I don't trust these numbers since I heard on the news about scammers calling and you call them back and your phone bill gets charged a fee. If you did call them back check your phone bill when it comes in!

Called on my cell phone, rang once, no message and hang up.

If you have a cell phone, you can add this number to your contacts, and set the ring tone to "no ring".  They can spend their money trying to call you, but you won't hear it.

They have called several times and have never left a voicemail.