How to turn off Cell phone function on iPhone 5

First let me be clear. I'm not talking about disconnecting my cell phone service with my carrier.

Onto the question:

I know how to turn of cellular data on my iPhone 5.

Settings -> General -> Cellular Data "Off"

But sometimes I need to turn off the Cell Phone function as well but still be able to use my device, uninterupted.

I know this sounds weird but it's true.

Any help would be appreciated.