Caller ID says "Running Spri CA". They leave no message.
I call back after business hours (using *67 to block my number). Their outgoing message appears to be a pretty good computer generated male voice. I hear, "Hello. None of our representatives are available right now. If you received a call from this number, we should contact you within the next day. If you believe you received this call by error, please, press 1 to be added to our Do-Not-Call list." (I never do this as it can actually make things worse) Note the failure to identify themselves. A computer generated voice makes me doubt their skill with English.
So they spoof their caller ID, leave no message, and fail to identify themselves. Smells like a SCAM.
I've heard this message from about half a dozen numbers. This is generally associated with scam fundraising. With other numbers I have seen this message associated with: National Patrolmen's Foundation (several times), credit card rate reduction scam, autism awareness, stop abortion, and a save the Cambodian Forest fund. IMO, none of these are legitimate charities.