Same...

Was a number  unfamiliar to me with "San Antonio" as the caller id.  (Tells me nothing about the caller.) I blocked it right away, right in the middle of the third ring, with one click on my phone blocker, and then checked it out here.. Based on the  two posts above, I'm betting it's either a start-up scammer, or an old, established one with a new telephone number.

I answered and it was a machine saying I qualified for a free trip. Hung up before it finished its spiel.

Called back and got "busy" signal??? SCAM

You can block the number, but it won't do much good.  These numbers are generated by a program and aren't real numbers.  They simply and randomly select numbers to send robo calls out to solicit individuals.  Sometimes, if you don't have VM or a service that picks up calls, the program might simply deem your number as "dead" and not call it again, otherwards...you're stuck like anyone else.  You can block it and just delete it, but the solicitor will hit you again with another random number.  Basically, its a way for them to get around from being tracked.  All it does for us is to become a pain in the [***] and a form of harassment that has no boundaries.  The calls could be from anyone, or entity, even politicians.