Same thing happened to me; rang once and hung up. With a 312 number, I thought maybe it was a company in Chicago that I applied to, but I never got the chance to answer the phone.
The message said something about a prescription benefits card. Since I'm not on prescriptions, I'm guessing they were trying to sell their card. The message said you had to make less than $65K & not be on Medicaid (or Medicare...I wasn't listening well at that point, and was hoping there would be an opt-out, but there wasn't.)