Credit Scam Robocall From Invalid Number

We use a third-party blocking service that intercepts calls from known spam numbers after one ring.  This call rang more than once with CID name string exactly "Name Unavailabl" according to our carrier's logs.  I picked it up after a couple rings but said nothing and put the phone on mute.  A recording (woman's voice with generic American accent) started playing immediately about my great credit card payment history and how it made me eligible for something or other.  It said I should press 3 if I'd already completed the process or wasn't interested or press 1 to speak with an operator.  I didn't press anything, just left it there muted.  After a few seconds a different, robotic sounding female voice said "Goodbye" and disconnected.

I looked the number up in an online reverse directory and found they have no record of it being assigned.