This is (likely) Express Scripts calling you about the status of one of your prescribed medications that they are trying to fill but are unable to do so without your assistance (i.e. need to send them a refill prescription request, get your doc to do so, etc.).

This was indeed a legit call from Express Scripts (there was no caller ID) so I hung up when the recording asked for my date of birth.  I don't give out personal information to incoming callers because there is no way of knowing who they actually are.  I then called Express Scrips back at their listed number (800) 282-2881 and they verified that they were, in fact, trying to reach me about a prescription refill that needed my attention.