Tap 
at the bottom of the screen to display the Settings screen.
You can change ringtones, call sound quality and also turn on/off the keypad touch sound.
Video Calls
Video calling function is available.
Click here for details of the video calling function.
Point-Paid Calls
Point-Paid Calls function is available.
Click here for details of Point-Paid Calls function.
About Call Sound Quality
If you select "Low," the sound quality deteriorates but interruptions will get less.
If you find calls interrupted, please try "Low" sound quality.