Mail your payment to: McLaren Bay Region, PO Box 68, Bay City MI 48707 Pay in Person: Cashier office hours Monday - Friday 8 a.m. - 4:30 p.m. Admitting can take payments during cashier off hours. Please direct billing questions to: Patient Accounting 989-894-8888 or 888-899-1077.Office hours are Monday - Friday 8 a.m. - 4 p.m. Emergency Department Physician billing - 888-952-6772; fax: 330 ....