When you're not getting calls, the first place to look is at ringer volume. To make sure that the ringer isn't muted or turned too low, on most mobile phones you tap the volume rocker on the side of the phone when you are on the home screen. You can also explore your Sound & Vibration options and choose your own level so that you will never miss an important notification again. If you're in noise a lot of times, sometimes the "increase ring volume" setting might be of assistance.