Review on AT&T TL86009 Cordless Handset, Black/Silver | For Use with AT&T TL86109 Expandable Phone System by Emanuel Frison

I have four of these phones. I bought three new and recently bought one used. New came "unregistered" and logged into the database normally. Used arrived pre-registered at another base. It refuses to recognize commands from my database, including the unregister command. Disconnecting the battery from the handset will not work because the registration information is stored in non-volatile memory. The manual and online FAQs don't solve this problem, instead providing brain-dead information like "make sure the base isn't too far away" or "make sure there's no shortwave interference", etc. In particular, it doesn't seem like any to give documented procedure. for the customer to factory reset this handset if there is no registered base station. There are no reset holes and no documented secret decoder key sequence. I have a request for AT&T support, but I doubt a phone tech can solve a problem that isn't covered in the manual. I'm not the only one with this problem. See here: [.] Update April 15, 2013: To my utter shock and amazement, AT&T Tech Support provided a secret decoder keystroke to factory reset the phone. These are: (right softkey "-") * 3 3 1 7 3 4 # (left softkey "-") The handset then beeped and restarted! I'm increasing my rating from 1 star to 4.