HI, I have a friend who has got a second hand yealink T41P which is locked to BT. When we try to factory reset it, it asks for the admin password, but it not the default. I have tried to change the firmware but it doesn't accept the new firmware. The pre installed firmware is a .rom file so it can't be over ridden, and the firmware is also customised. Is there any way that I could get the password to reset the phone?