I called this number back from my cell phone and the recording said, "you have a reached a non-working number for Aetna, please call the telephone number listed on the back of your health insurance card.". Suffice it to solve the mystery. However, why didn't the caller leave a voice mail message?
This is a legit number from Aetna's call center in Blue Bell, PA. There are a number of departments located in this office: EAP services, case management, etc.