I will try to be as detailed as possible.
I have one line for calling and receiving calls, when the phone rings the number 1 lights up on the soft buttons and when i call someone the number 2 soft button lights up. The problem appeared all of the sudden so i don't know if some button was pressed by accident and messed up with the programming.
As i said when i have an incoming call the phone rings normal as usual, i answer the phone and for 3 seconds i can talk and hear the other person. after the 3 seconds the line cuts off.