If the sound of OPPO mobile phone is very low, it is suggested to deal with it in the following ways: 1, click the phone volume+button to turn the phone volume to the maximum; 2. At this time, if the call sound is still too low, click the volume change icon that appears; 3. Open all the volume adjustment charts at this time, and you will find that the volume of the system is not loud enough. At this time, you can increase the system volume. 4. If the above method doesn't work, check whether the receiver is blocked by dirt and clean it up. If it still doesn't work, it is recommended to take the phone to oppo customer service.