Do you mean the Panasonic KX-TGF370 base for a cordless phone system? Depending on the number of handsets, the model number could be KX-TGF372 or KX-TGF375. This base also came with the KX-TG585SK.
From the handset to clear the blocked call list, press the Call Block button (below 0). Use the up/down arrows to choose whether you are dealing with a single number or a block of numbers. Press the soft key for Select. To erase one number, scroll through the list to the number to remove. Press Select and then choose Erase. Confirm this by highlighting Yes and pressing Select. Press Off to leave the menu system. To delete all of the numbers in the call block list, press Menu (see the LCD screen label for the soft key) after choosing the Call Block single number or block of numbers option. After pressing Menu, use the arrow keys to choose Erase All. Press Select and then confirm the choice twice by choosing Yes and pressing Select each time. Press Off to exit the menu.
From the base, press Menu (center soft-key) followed by # (below 9) 2 1 7. From here follow the directions above, with one exception. Press Exit to leave the menu system. You can press Menu and then navigate through the menu with the arrow keys to choose Call Block and press Select.
These steps are shown in the manual available from the Panasonic product page: https://shop.panasonic.com/support-only/KX-TGF372S.html
. The current link to the manual is ftp://ftp.panasonic.com/telephone/om/kx-tgf372_en_om_.pdf . See page 34 for the complete directions; page 45 shows the section of the menu tree.
I hope this helps.