Bin it! Not much help, I know, but the best advice available. When this phone set fails it's always the answering machine that packs up in one of two ways: (1) permanently screeches and beeps when a message is received, (2) locks up the answering part. One solution is to press the Play button and keep it depressed till the machine says 'You have xxx old messages'. Listen to them, or press the forward key, and at the end, when prompted press the 'Del' key AND WAIT FOR THE BEEP! If you fail to wait for the beep the messages will never be deleted. As far as the reset codes go, BT phones seem to be designed to become landfill! Higher end brands often have factory reset codes on their support pages but as far as I know, and I've looked in vain, BT don't publish them, or they never existed in the first place. As I said, destined for landfill!
BT Puzzeler, March 2009