The only way that you can receive a phone call when you aren't in your "home cell" is that your phone sends a ping to each cell you enter to let the system know where to route any incoming calls.
You don't have to make a call from the new cell, your phone sends the ping on its own. Whether your phone has to be powered on, or just have the battery intact for this to happen, depends on the cell phone.
I’ve heard this repeated by others, including Rush Limbaugh, but cannot find a single technical source to prove it. If you know of a cell phone that can communicate with the cell system even when turned off, would you please pass the information along? Thanks.