My wife called the last 3 times I had to do 90 days to the service number of Immigration. The officer told my wife that they are working on the problem.
Online does not work in the last 2 years for me. But: you do not have to go yourself to the office. You can send somebody to do it for you. I do that already for 3 years.
They do not switch any extension before the due date is near. I tried to change my extension (based on a work permit) into a marriage halfway halfway: no way. I had to wait till the end date of my visa.