How do you get the KX-TGA270S apart to replace the Antenna

see manual you must put it in the samme frecuency

There is a section on setting the number of rings in the manual for the base unit on page 28. You can download it from here: http://www2.panasonic.com/consumer-electronics/support/Phones-Fax/Telephones/Expandable-Systems/model.KX-TG2740S

you dont need to deregister it if you have not registered all 8 hand sets with your base unit. Just register the new one and the base will assign a new # for this new. I you had registered 8 hand sets with your base already, you need to remove(deregister0 one handset from your base(it can take only upt 8).
If it still not registering please deregister as follows:
on the base unit, press program, them mute, then enter 335#, then enter the handset number you wish to deregister.
after deregistering try to register your new hand set.

I have a Panasonic Multi-talk KX-TG2740 and I need to change the outgoing message. Anyone know how to do this? (There is no "greeting" button as mentioned below).

Thanks!

press function, initial setting, registration, deregistration, enter 335(deL) and then press Ok (right button on screen).
Once that is done press mute on the base unit and Ok on the hanset (right button on sreen)

IT IS DUE TO FAILURE OF ANTEENA

IT IS DUE TO NETWORK FAILURE OF THAT LINE

Hi - You can download the manual from the link below:

kx-tga270s



Please update the question & let us know if the information given was useful to you - Good Luck!

http://ec1.images-amazon.com/media/i3d/01/A/man-migrate/MANUAL000002171.pdf

Above is link to Operation Manual. See page 65

For Panasonic system (especially for KX-T7633), you have to make changes from extension 101.
1. leave handset in the cradle then press "program".
2. Dial *# then "SP-PHONE" button until you see something like time set something something
3. manually input correct date then time then press "auto dial/store" button.
4. pick up the handset then hang up to save.