They've called like 4 times now and they never leave a message.

I've gotten two calls from them, and no message.

I suspect this is the MSU alumni association.  They occasionally contact me to donate money for YEARS and always from a 517 number. I stopped answering calls from that zipcode unless I'm expecting a call.

This number has been calling every day after 6p for the past week.  They never leave a message.  Must be MSU based on the previous comments.  If they want money, they are barking up the wrong tree.  I donated money to the CVM until they got rid of our favorite critical care vet.

I too suspect it is from the MSU alumni association.  Historically, they have attempted to "get" some of my money.
Maybe next time they call, I will tell them I have died and no longer available to donate money.  Think that will help?  Maybe not.