No message is ever left. I suspect this is a spoofed telephone number - probably automatically shows a number based on where you are located so you'll think it's a local call. I'm nowhere near the 720 area code.
My office has received multiple calls. They always want to verify contact info and names and tell me that 'this call will be recorded' and want me to authorize a subscription and provide my name. I continuously offer to transfer them to the person they actually want (CFO), but they decline as they "work in a call center and can not leave messages or receive calls back". I am starting to get annoyed.