Navigate to the Admin panel and click on "billing" and you'd be redirected to a new interface. Click on the "change plan" and you'd be redirected to a new interface with a drop down menu to choose your new plan. Choose your new plan and click on the "Change subscription" button. You'd be redirected to a Flutterwave interface to make an additional payment if you're upgrading your current plan and if you're downgrading your plan, it would change automatically once the "change subscription" button is clicked.