I think there is a significant chance that the call came from a collection agency, but without more details from you that is just an educated guess.  They have phone service with a provider used by many CAs, and leaving a file, reference, code, or other number is common practice.

r
Received a call on my cell from this number. They did not leave a message. I know no one in Oklahoma. They left a code for my cell number. Don't know what that is about. I did not call back.