Increasing the Signal

I didn't know there was such a thing as a cellular booster. Some of my clients complain that they couldn't contact me at times. For some reason, the signal of my cell phone would get lost or get weak in certain areas of the house. I was told by one of them to get a cellular booster, a gadget that boosts cellular phone signal.

I did my research and it turns out that the gadget is inexpensive. The question is, does it really work?