This sort of work is most likely done by your IT staffer or calling in a phone technician as what I found online was lacking to exact details. Maybe this system has been discontinued for too long?
https://www.tlc-direct.co.uk/Technical/DataSheets/Panasonic_Systems/PA308_Getting_Started.pdf seems to agree you only get 3 plans.
I've a Panasonic KX-TEB308 to drive 4 internal phones, no external lines, very simple configuration.
I would like that the first connector will be assigned to dialling number "1", the second to "2".. and the forth to "4". The phones have to call each other with one key, it seems impossible cause the Panasonic Maintenance Console software has only 3 preconfigured plans and doesn't allow to add a new one, how could I overcome this?
I would know what other settings I've to add to a "vergin/just resetted" PBX ho have the 4 lines working in this way. Thank you really a lot for your help!