Follow This Simple Steps -:
1) Firstly Download Random Ringtone Manger [ Click Here ]
2) Open It And Now Start doing Setup
3) In First Tab you will see the option of Ringtones there, Simply Click on Any Ringtone and it will start playing as preview, then tick on it.
Tick as many ringtones you want to Set as your Ringtone and you are done.
4) Now you will always Hear Random ringtone when you get any call from Someone.
Enjoy..... ...