Re: cancelling health insurance
I sent my health, fire, and home contents insurance companies each a letter and enclosed a copy of my deregistration from the commune (Attestation de départ). On the advice of my agent Jenny of this forum, I wrote the letters in English, and it wasn't a problem.
I included in my letters: my name, date of deregistration and departure from Switzerland, insurance policy number, Swiss address, email, and phone number, and my new contact information (address, phone, email) in the USA, specifying the dates I could be reached in CH and in the USA. I also included my bank account information for refunds.
Within about a week or two each company sent me a written confirmation by post confirming my cancellation and letting me know about refunds, if any. Jenny had suggested I follow up my letters with a call after about a week; the only one I hadn't heard from within a week was my home contents insurance -- I called but their confirmation letter came the next day.