received call on caller I.D., no message

Called back and it is not a working number.

Received call from this number. They didn't leave a message. I called back and the number is not in service. How's that possible? Technology...

Received many calls from this number all claiming to be able to give me a discount on my electric bill due to deregulation.  Got another call today, this time from 845 776 3553 and was able to verify this is a scam trying to find out my electric account number.