Why does someone call oppoR9 without prompting?

R9 enters Settings-Telephone-Vibration to prompt the other party to connect/hang up, and this function can be turned on and off.

Set the waiting path of mobile phone call:

1.coloros version 3.0, enter Settings-Telephone-Operator Call Related Settings-Other Settings-Call Waiting;

2. Other ColorOS versions, dial-call settings-other settings-call waiting;

3. Non-ColorOS version, Settings-Call Settings-Other Settings-Call Waiting.

If the call waiting switch is turned on to prompt a network error, and the call waiting service is not enabled on the mobile phone card, please contact the operator to enable it. (Unicom phone 100 10, mobile phone 10086, telecom phone 10000).