If you got a letter from MI, then I would say call the tax department, at the number at the top of the letter.
Before you do, though, look at your return and make sure there's nothing inadvertently classified as a military pension or railroad benefits.
You can look at all your 1099-R worksheets to make sure the box RRB-1099-R at the top isn't checked. If it is, explain to them that it's not.