This is an internal phone number for s company that serves the pharmaceutical company Astrazeneca (for their AZ and Me program) and RX Outreach. Their contact number for people calling in is 800-769-3880. This is a legitimate caller, and most likely you are a family member is receiving prescription medications either directly from these companies or via your doctors office.
I received a message to call back to their 800 number. I could understand why they may not leave a message due to privacy concerns.