Major problem.. please help

No, but $50 buys a used Panasonic Key Service Unit to plug the phones into and get EIGHT intercom extensions.

In programming you can set up Forced account codes for Local, Toll, or All calls. The extension is flagged in program 605 or 2.1 of the system and the codes are put in 310 or 1.5. It's one of 2 ways you can do it, you can also change Class of Service on each phone to deny them access to certain numbers.

Keep in mind that this is programming for a TA-824 release 3.0. We know loop start CO lines and no ISDN or BRI. Your system may be different.

Carl

If you are using the KX-T7730 phone on a Panasonic KX-Txx 308 or 824 system.
From the Switchboard / Main telephone ( usually ext 101, 10 or 9 ) with the handset on the cradle/hook :
1. Press PROGRAM * # followed by the system password ( default is 1234).
2. Now press 604 and then SP-PHONE. Enter the jack number you wish to change ( 01 is extension 101, 02 is extension 102 etc. ).
3. Enter the name ( basically the same as texting on a cellphone ). Press AUTO DIAL / STORE to save your change.
4. To go to the next extension press SP-PHONE. Don’t forget to press AUTO DIAL / STORE to save your change after each name entered.
5. Press PROGRAM to exit program mode and you are done.

If you are using the KX-T7730 phone on a Panasonic KX-Txx 308 or 824 system. From the Switchboard / Main telephone ( usually ext 101, 10 or 9 ) with the handset on the cradle press PROGRAM * # followed by the system password ( default is 1234). Now press 604 and then SP-PHONE. Enter the jack number you wish to change ( 01 is extension 101, 02 is extension 102 etc. ). Enter the name ( basically the same as texting on a cellphone ). Press AUTO DIAL / STORE to save your change. To go to the next extension press SP-PHONE. Don’t forget to press AUTO DIAL / STORE to save your change after each name entered. Press PROGRAM to exit program mode and you are done.
PLEASE rate / vote this answer if it was helpful.
Thank you.

I assume that you want to program the extension names.

If you are using the KX-T7730 phone on a Panasonic KX-Txx 308 or 824 system. From the Switchboard / Main telephone ( usually ext 101, 10 or 9 ) with the handset on the hook/cradle press PROGRAM * # followed by the system password ( default is 1234). Now press 604 and then SP-PHONE. Enter the jack number you wish to change ( 01 is extension 101, 02 is extension 102 etc. ). Enter the name ( basically the same as texting on a cellphone ). Press AUTO DIAL / STORE to save your change. To go to the next extension press SP-PHONE. Don’t forget to press AUTO DIAL / STORE to save your change after each name entered. Press PROGRAM to exit program mode and you are done.
PLEASE rate / vote this answer if it was helpful.
Thank you.

You have to go to your phone switch, I believe that all Panasonics are modular connectors. Look for a label that will correspond to your extension number. Find your other extension and then unplug and plug.
Cheers.

The side buttons is programmed as extensions
To change the extension names follow these steps :

If you are using the KX-T7730 phone on a Panasonic KX-Txx 308 or 824 system.
From the Switchboard / Main telephone ( usually ext 101, 10 or 9 ) with the handset on the cradle/hook :
1. Press PROGRAM * # followed by the system password ( default is 1234).
2. Now press 604 and then SP-PHONE. Enter the jack number you wish to change ( 01 is extension 101, 02 is extension 102 etc. ).
3. Enter the name ( basically the same as texting on a cellphone ). Press AUTO DIAL / STORE to save your change.
4. To go to the next extension press SP-PHONE. Don’t forget to press AUTO DIAL / STORE to save your change after each name entered.
5. Press PROGRAM to exit program mode and you are done.

try 408

If you are using the KX-T7730 phone on a Panasonic KX-Txx 308 or 824 system. From the Switchboard / Main telephone ( usually ext 101, 10 or 9 ) with the handset on the cradle press PROGRAM * # followed by the system password ( default is 1234). Now press 604 and then SP-PHONE. Enter the jack number you wish to change ( 01 is extension 101, 02 is extension 102 etc. ). Enter the name ( basically the same as texting on a cellphone ). Press AUTO DIAL / STORE to save your change. To go to the next extension press SP-PHONE. Don’t forget to press AUTO DIAL / STORE to save your change after each name entered. Press PROGRAM to exit program mode and you are done.
PLEASE rate / vote this answer if it was helpful.
Thank you.

If you are using the KX-T7730 phone on a Panasonic KX-Txx 308 or 824 system.
From the Switchboard / Main telephone ( usually ext 101, 10 or 9 ) with the handset on the cradle/hook :
1. Press PROGRAM * # followed by the system password ( default is 1234).
2. Now press 604 and then SP-PHONE. Enter the jack number you wish to change ( 01 is extension 101, 02 is extension 102 etc. ).
3. Enter the name ( basically the same as texting on a cellphone ). Press AUTO DIAL / STORE to save your change.
4. To go to the next extension press SP-PHONE. Don’t forget to press AUTO DIAL / STORE to save your change after each name entered.
5. Press PROGRAM to exit program mode and you are done.