Turning off 3G on iPhone 5

Hi there everyone I was wondering can anyone tell me if it is possible to turn off the 3G on the iPhone 5? When I go into Cellular I see the option to turn off the 4G but I don't see any 3G toggle. Also was wondering when I am at home on WiFi noticed that when it disconnects sometimes that 3G is already on does this mean that they are both running at the same time?

Thanks for the help.