Robo call said "Goodbye".

Didn't leave a message.

Robo call says "goodbye". Telemarketer spam confirming phone number. Ignore.

Same here.  A recording saying "goodbye".  Probably a probe to see if the line was real.  415 is San Francisco.

Called and actually got a human.  "This is Eugene with NCA."  He said he wanted to speak to the owner of the business. I said I wouldn't speak to him until he identified NCA.  I had to keep pressing by telling him I wouldn't continue the call until I knew what NCA was.  He said it was National Credit Adjusters.  It's a debt collection agency.  Here are some reviews on them:
https://www.consumeraffairs.com/debt/national_credit_adjusters.html

This is from Florida and includes information about law suits filed against these "people" by other states:
http://www.floridadebtfighters.com/fdcpa-righ ... -adjusters-llc/