- Open the "Settings"
- Select the Sound option.
- Select "Ringtone."
- A choice between SIM1 & SIM2 appears at the top of the screen, select the desired SIM card.
Press “Ringtone”, select the desired ringtone for SIM1 and press OK. Similarly for SIM2.
Also, these options can be here: Settings—> SIM-card management
You can also use the free DualSim Ringtone app.