Zte T230 User Manual page 25

MUTE A CALL
During a call press the power key briefly to light up the display, then
press the Mute button or Options > Mute to mute your microphone.
The mute icon is displayed.
MAKE A CONFERENCE CALL
A conference call can be made between yourself and two or more
other parties.
During a call press the power key briefly to light up the display, then
press Options > Conference
 Call the first number.
 While you are connected, tap Add call.
 Call the second number.
 While you are connected to the second number, tap Merge
 To add the third party, tap Add call.