Since yesterday, I have disabled mobile internet on my phone since my data ran out. Just a while ago when I connected my mobile to laptop to sync with Zune, I received mail on my phone. Later I browsed Internet Explorer and WhatsApp. Everything worked great. Therefore, I rechecked the mobile network to see if it was off. And yes, it was still off.
Then I realized it might be using my laptop connection which is connected to a LAN network for internet browsing.
So, my question is what happens to mobile internet connectivity when it's connected to a laptop. Does it automatically use any available net connection from the laptop, or just the via-LAN internet?