I am really pissed off at Sanitas at the moment.

They continuously screw up my bills every month. They give me until the first of each month to pay a bill, then they send the next months bill around the 22nd of each month with it being doubled because I'm in arrears on their computer.

That's not so bad. I can get used to that. Then I get a letter yesterday asking for 8 months of premiums from the 4th of January the end of August

Granted I screwed up with getting the insurance for my wife. She arrive in January and I didn't start her policy until March. So the Canton picked up on this and insisted I give money to sanitas for this time. So I was expecting a bill for 4.01.10-28.02.10 + the month of August.

BUT nooooooooooo they have to give me a bloody heart attack wtih a bill for 1300CHF

Why can't they get their billing sorted? I have been paying my premiums for all these months reliably and on time, only for them to consistently screw things up?

Now I need to call their equally incompetent call centre staff who don't understand a word I say.

rant over

What about a standing order?

I actually ticked that box when I sent away for the insurance but they ended up sending me the orange payment slips every month. That's how incompetent they are.

Sounds like you need to change insurance companies. Go to www.comparis.ch and do a little comparison shopping. Send Sanitas a registered letter no later than Sept 30 saying you are outta there at the end of December. I think there are even sample letters on comparis for this. I have used Swica and Visana and had nothing but good experiences.