Caller ID says "Test Code         PA"  and is a hang-up.  Any ideas?

I just got the same call with k
no message and earlier they called my cell number.

called my number and hung up, no message.

It is called "mocking" ;your telephone is being used as a mock object. If you call back , a computer string of info is released to thaat "dummy" telephone account number. Just call once and they have the info that they need. I got a call ,too. I reported it to the Fcc, but it this system is also used by the govenment, too. Be careful.

My caller ID revealed only the number; no name was shown.  I did not answer the phone.  The message was from an electric company offering a discount on my electric bill.