These people call every three or four days and hang up as soon as they are told the person they want to speak with is unavailable and they hang up without leaving a message or stating the name of the company for which they are calling.
My company does not take solicitation phone calls - which I recognized this as one right away - told him my boss would not be wlling to take the call and to not call back - but what did he do... He called back to argue with me so I hung up on him again.