TT Systems 3460 2.4GHz Phone (IBM-3460) "erase simple tech" Questions

...simple voice menu is as follows: ? Press "#1" to play mailbox 1. ? Press "#2" to play mailbox 2. ? Press "#3" to play mailbox 3. ? Press "#5" to stop. ? Press "#4" to repeat the message. ? Press "#6" ...

...simple one. How do I erase one or all stored phone numbers from the memory? I just want to erase them, without replacing them with new numbers. I have tried removing the battery and unplugging the ...