Who called from 7206397966

Somebody keeps calling but does not leave any message.

Calls to this number, no company id on caller id, no messages left. call back number and it says that no one is  able to take my call, if you feel that you were reached in error please press 5 to be added to our do not call list (but takes 48 hours).

called again caller id just says denver colorado, no message and i already told them they had reached this number in error.

This number called again today, no one on other line, when or if you call back you get a recorded message saying that no one is available to take your call, but if you feel you recieved this call in error press 5 to be added to our do not call list, right that helped to get me called again. no company name on called id just said denver colo,
i am getting tired of getting these types of calls earlier it was a cold sales call from a security company wanting the house to be advertising house (first of all i rent) and it was not the first call from one (2 in last several days)

love to find out who this calller is so i can give them a piece of my mind