Solution:
1. The echo heard during the call are caused by network problems in most cases. It is recommended to change the network environment, or to call in a different place. This can generally solve the issue.
Note: The network environment problem does not specifically mean that the mobile phone signal is weak, and the echo during the call is generally independent of the signal strength of the mobile phone.
2. Try backup, restore factory settings, and try to call when backup is not restored.
3. Update to the latest version of the system.
4. If the above methods fail to solve the issue, it may be due to a hardware problem. It is suggested to go to after-sale center for inspection.