You might gain some insight by reading that, and also by actually providing the specific model number <ahem>
Seriously though, Panasonic makes a gazillion different cordless phones. That's why we need more specifics.
The Panasonic DECT cordless phone can extract the telephone numbers from a bluetooth connected cell phone. Is it possible to load numbers into the DECT phone from another source, e.g., a PC? The connection might be the same bluetooth link the cell phone uses.