Caller ID says "FIRE CHARITFUND".  They call twice in one day about 8 hours apart.  Each time they leave no message.

I call back after hours (using *67 to block my number).  I hear the following, "the number you have dialed is not in service.  Please, check the number and try again."

So a spoofed caller ID and the inability to be called back.  Smells like a SCAM.

Paul-C reported that it was something like "Fire Fighters Charitable Fund".  There is a "Firefighters Charitable Foundation".  Charity Navigator gives them 0 stars and says at very most 7% of your donations do anything positive,  When I googled that name, someone listed them as #5 on America;s Worst Charities.