Caller ID says "Waltham MA". They leave no message.
I call back during business hours (using *67 to block my number). I hear the following, "Hello and thank you for calling. If you'd like to be placed on a Do-Not-Call list for the number that called you, please, press 1 now."
So we have a spoofed caller ID and the failure to identify themselves. This smells like a SCAM.