Terminate my health insurance

Hi I moved to Switzerland less than 2 months ago and was supposed to stay here until the end of the year. But for professional reason, it seems that I will be leaving next month. I did sent a signed contract to Assura a couple of weeks ago but I haven't received any reply from them. Is there a way to terminate the contract? (provided that they have received my letter). If not, do I really have to wait till the end of the year and keep paying?! Any way to break it if I am no longer living and working here? Thanks for your help