I swipe the phone to "answer" but don't say anything to see if a machine is going to click in and say something. This time an automated voice said "that is not a valid extension" as if I'd made the call to them. I'd say this is a robocall spammer, by the face of it.

I did not answer this number, did not recognize the area code, they left no message.

Received a call from this number. It rang once then called again with an African country code in front of it. Total spam call of some sort.

Just got a call from them.  Didn't answer because I wanted to check the number here first. My call logs say this is the first time this number has called me, BUT... I noticed in the past week I'very gotten calls from unknown numbers where the area code has been incrementing. In other words, in the morning I'll get a call from area code 314 and in the afternoon it will be from area code 315. The next call will be from area code 513. Haven't checked but the exchanges  (the next 3 numbers) appear to be random and I suspect some of them are invalid exchanges, i.e. not yet in service. Definitely a scam.

No caller ID, so didn't pick up. No vmail left. Now blocked.