How to adjust oppo SMS without ringtone?

Take OPPO R9S mobile phone as an example, the setting method is as follows:

First, click "Settings" on the desktop of OPPO R9S mobile phone.

2. After entering the setting interface, select the "Sound and Vibration" option.

Third, then find the SIM card to set the information ringtone. Take China Telecom 1 as an example, and click Enter.

Fourth, after entering, select the ringtone to be set.