Out of curiosity, who is the utility, if you know? Peco? If it's Peco, call their consumer relations department on Market St. Better yet, send them a certified letter.
A couple of other questions: Do you have caller ID, and if so, does the phone number show up on it?
You may want to try the PA Attorney General's
Office, or like Steve said, the PUC.
Of course, if you want to spend a few extra bucks a month, and get rid of more annoying calls, get Call Intercept from Verizon.