It definitely is PNC calling. You can call the number back. Anytime your payment is late or if a electronic transfer did not go through, they will call you. Sometimes up to 7 times that day. If you have doubts, call them from the number you have on file with them and they will let you know why they are trying to get a hold of you.
I have received several calls from this number and when I answer, there is no one there. I hit redial and they answered "pnc may i have your account number?" This is not a debt collector as all my bills are paid on time. I just told the person "you aren't tricking me" and hung up. The banks tell you never to give out your account number and also that they will never ask for it. As far as I'm concerned, it's someone out there scamming innocent people.