Go for either LycaMobile or Lebara, both of these are for low cost calls to India. Do note that local calls in these are expensive.
Additionally, if you really talk a lot to India, you could do this:
1. Buy a Sunrise phone with Sunrise Flat connection. With this use can call any landline/Sunrise number in CH for 1 CHF per day.
2. Buy a Teleline(
www.teleline.ch) flat Calling card at 20 CHF/month, and use it with the Sunrise number. With the Teleline card you can call India as much as you wish to.
So effectively at 50 CHF/month you can call India as much as you like.