Best answer by Daniel Kim
Do you have a tab that needs to be paid off Danny? As you won't be able to change to the lightweight plans until you pay off your tab.
Also try refreshing your browser, clearing cache and cookies and see if that works.
If you're still not able to see the lightweight plans, you can call koodo and have them change the plan for you at no charge since you already tried via self serve. *611 from your koodo phone.