I generally don't answer these calls. This time I answered the "seller" who claimed to be part of an energy company (I don't remember the name). But it was to tell me that I "qualified" for their program. It's a sales pitch and I hung up. If I didn't answer before and tried a call back, I'd get the same thing: "This number is not in service." It's a new method of making sales calls.
(Yep. Just tried to call back the number and "it's no longer in service".)
Next time, I'll blow a whistle into the transmitter. Maybe they'll eventually get the hint.