There are plenty of decent iPhone cases on the market. The mJoose Signal Amplifier Battery Case does more than most though. It protects your iPhone 6s and boosts its signal by 100x. It is compatible with AT&T, Verizon, T-Mobile, and other top carriers.
The case also extends your phone’s battery life. It works on 2G, 3G, 4G, and LTE bands. Worried about radiation exposure? This case can address that too.