The problem is that the metal roof prevents microwaves from being transmitted from the cell phone towers as well as from the cell phones. There’s no foolproof way to avoid the annoyance of dropped calls, there are technological fixes available that allow for improvement in the reception and transmission of cell phone signals. You can also reduce background noise to some extent and achieve overall better sound quality. See more on metal roofing here
An electronics store should be able to sell you a cell phone signal booster and an external antenna. This is the most effective method of treating the problem. You’ll connect the power booster to the RF port of the cell phone. The cables should come with the power booster. The power booster will be plugged into an electrical outlet inside the building.
Now, connect your power booster to the external antenna. If the antenna did not come with a cable, you’ll need to purchase one. The store where you bought the booster should carry the cable you need.
Now, test it out by making a call. The signal should be at least ten times stronger than before, possibly even stronger.
The only catch in all of this is that if your phone does not have an RF port, this solution won’t work for you.
Actually, you can even use your booster in a car if you so desire by plugging it into the cigarette lighter.