When in the mitel server, Select what unit you will need
Unit 288 - Main Office
Unit 20 (Also Unit 21 and Unit 31)
M&M (M&M Office)
Lockerbie (Forestsawmills)
IN Devices , Phones. There will all the phones in the system for that office.
Firstly when setting a phone up try and find a extension number that is free. This will be named "Spare" or something simular
If there is a spare phone, Change the name and config the phone.
If there isnt a spare extension number. Right click and create 52x/53x (Does not matter if there is a x or x's in the number as they will disapear) And select a extension number close the what the phones have etc, If the office have extension numbers 4000-4999 try and keep it in the 4000's
Select the extension number and create.
There will be a empty phone number for this now.
Change the name and config the phone.