You can select the ring tone you want to hear when you get a call.
Slide two fingers downwards starting from the top of the screen.
Press the settings icon.
Press Sound & vibration.
Press Phone ringtone & vibrate.
Press the required SIM.
Press Custom ringtone.
Press the required ring tones to hear them.
Once you've found a ring tone you like, press DONE.
Press the Home key to return to the home screen.