John C. Fremont Hospital Billing Office in Mariposa is Closed for Walk-Ins Due to COVID-19 – Offers Many Options for Payment Without Coming into the Office Details Last Updated: Thursday, 19 March 2020 10:56 Published: Thursday, 19 March 2020 10:56 View Comments March 19, 2020 - The John C. Fremont Hospital billing office is currently closed for Walk-ins due to COVID-19.Source: John C. Fremont Hospital View the discussion thread. back to top