How to Ringer On of Panasonic KX-MB772

Before adjusting volume, set the operation mode to fax
mode (page 16).
Ringer volume
While the unit is idle, press {V} or {^}.
L If there are any documents in the document
entrance, you cannot adjust the volume. Confirm that
there are no documents in the entrance.
To turn the ringer OFF
Press {V} repeatedly to display "RINGER OFF= OK?".
i {SET}
L The unit will not ring.
L To turn the ringer back ON, press {^}.
Ringer pattern
L You can select one of 3 ringer patterns (feature #161
on page 50).
Monitor volume
While using the monitor, press {V} or {^}.

and if it work then say a thanks to your Pakistani Brother.