This is a scamming realtor farming FSBO listings. He is trying to get you to convert your FSBO to him for a fee.

His name is Jerrold Collins. He works for Signature Realty Inc:

Signature Realty Inc.
11941 W 48th Ave #201
Wheat Ridge, CO 80033
(720)495-4846 Phone
(303)531-0033 Fax

He would only hang up when I threatened to pass him along to the Feds for a DNC violation. Persistent would be an understatement.

Put this number on your do not call and ignore list.