G'day waqar

Check these things:
First make sure the signal you are reading has enough current to actually sink (or source) the pins ... I don't know the limit but you should find it in the MCU documentation ... if the current is not enough ... put a buffer or trans on it so you can amplify the signal ...

If you're detecting the off mode (JB p2.0,$) make sure that you set the pin to 1 first (as Raghunathan said). also remember to put a pulldown resistor on the line because If you read 0v it doesn't neccessarily mean that it's grounded ... it could be in a hi-Z state (heh I know nothing about telephone protocols and states)

yeah if these two don't work, somehow check to see if the command is executed at all (using a LED or LCD panel or something) .. if it is executed you might have a blown latch or something ... try another port ... if not ... then theres something weong with the micro (probably) ...

cheers
Nima