For your information, a Test Code can be created by anyone; check the internet. It is a computer-base system that sets up a dummy ring to a phone. If the person calls this Fake tel number, it sets up a loop and a string of information about the individual who called. Do not call Test Code telephone numbers back. Any company, organization, or individual can create a mock object.
It could be "spoofing". Basically, someone routing a call to you through a discontinued tel number so he/she can't be traced. I got that a few days ago, too. Spoofing is something that the FCC suggests people report to them. I did an online file complaint, but you can call or mail in a complaint about being called from a disconnected number. The information the website asks for are very general: time of call (just look at caller ID), telephone number, the number you were called at, and the date. I think if you can't remember all the details they won't care. They just want to make people aware of scams.