Okay, I know nothing about the Kindle, but as far as I know Calibre doesn't automatically establish a connection to any nearby wireless (WIFI) device. So I'm not sure if you're asking how to:
- Disable Kindle's automatic connection to the internet in general
- Disable Kindle's automatic connection to Amazon
- Disable Kindles automatica connection to Calibre
Or perhaps I've completely misunderstood what you wanted?