Contact's Extension Number Not Showing

It seems that if I have a customer office number that is only on the customer itself and not documented on each contact, when viewing a contact for that customer - in a ticket - it will not show the extension number documented for that contact and will only show the customer “main” phone number. This is pretty common if there is one main phone number for the company and I want to have that number under the customer itself and when I add contacts I just want to add their extension number. And even better if I only have a mobile number and an extension number listed for the contact, it will show the mobile number as the phone number associated with the extension.

Ideally I would like to see 3 fields 1) customer “main” number (listed as customer office number on “customer info” field) and should populate the extension associated to THIS number 2) contact direct number number 3) cell

Am I missing something here?