Mich. Comp. Laws § 750.507

Sec. 507. Every telegraph and telephone company operating in this state shall give priority to emergency messages or operator-handled telephone calls directed to any public safety agency and the person responsible for failure so to do shall be guilty of a misdemeanor. For the purposes of this section, public safety agency means any fire department, ambulance company, law enforcement agency, civil defense communications facility and the department of military affairs.