I know this is old. :) but I want share for the sake of sun users. 

Hi guys! I am a new Sun Cellular subscriber and the signal is terrible whenever I am inside our house or office. So I have took look for a good spot or roam around to stable a good signal.

Since Sun is now with Smart, I tried to change the network manually than automatic.

Boom! The signal is up and able to establish a 4G signal higher than I expected..