Originally Posted by pleh.yoogle
I had difficulty finding the setting for this feature since you have to navigate to the wifi calling app, then hit the menu button below the screen. Select settings, connection preferences and select wifi. To get this menu, wifi calling must be enabled though. post if this fixes your problem.
HTC Sense has widgets to switch on and off mobile data and wifi (amongst many other things). Just put them on one of your homescreens.