Talking on the cell phone and driving is against the law in most states and for good reason because talking on the cell phone while driving distracts the driver and can cause wrecks and even fatal wrecks.
When you're on your cell phone your attention is on the phone and not on the road where it should be so you're able to react in time.
Michigan however doesn't have any laws that prohibit cell phone use while driving so it's legal in Michigan to drive while talking on a cell phone however you really shouldn't talk on the cell phone while driving anyway because although it's not against the law it's still not safe to do so.