Hi all,
two years ago I arrived in Geneva and got an insurance with Sanitas. After three months I moved to the French side, but I continue working in Geneva that's why I kept my existing contract with Sanitas.  I was paying my premium as before, but now Sanitas asked me to pay an increased premium because I'm a frontalier. And they do ask me to pay also the difference for the last two years. I never went to a French doctor and I plan to visit only medical doctors in Geneva as before.
Is there any legal way that I could avoid paying this money?

Any help or suggestions are highly appreciated.
Yannis