I have a Sharp FX Android phone.. I went to connect to my local router through the Wifi Options.. and at the top of the Phone the 3G symbol is still there.. As well as the Router Bars.. However the only thing i did notice.. is When the Wi-Fi was turned off.. The 3G had an Up and Down arrow next to it.. And with the Wi-Fi enabled The 3G had a blue "V" appear below it..

Will I still be Charged through the 3G despite that I am Connect via Wi-Fi?