Must be some robo dialer calling my unlisted cell number. Call blocker intercepted it.

Something about student loans which I have never had.

Calls a couple of times - and tells me about student loans or other things I'm not involved in nor interested in..

I  have also had calls from this number, which I don't answer, but once I did try to call back and it came up "Not a working number"!! How do they do that?

Caller ID Spoofing:

https://en.wikipedia.org/wiki/Caller_ID_spoofing
https://consumercomplaints.fcc.gov/hc/en-us/a ... ID-and-Spoofing
https://www.fcc.gov/guides/caller-id-and-spoofing