I received a phone call from this number and they didn't leave me a message. no idea who this is

This number 720-545-9027 belongs to a collection agency.
Diversified consultants

along with 7204658111, (800) 771-5361

Diversified Consultants, Inc. Memberships and Certifications
We are the nation’s ONLY telecom-specific collection agency specializing the in the bad debt recovery of Wireless, Landline, Cable, Satellite, Utilities and Security arenas.

WEB URL
http://www.dcicollect.com/

No easier than blocking these #'s with your blocking service; go to apple store apps section.