Yes, you can! Go to your "My Plan" page then click on "upgrade my plan" link (you can both upgrade or downgrade) and choose a plan that is best for you. The change will take effect immediately.
Note: When you make any change (upgrade or downgrade) in your current plan, we will refund you the for the remaining credits on a pro-rata basis and a credit note is generated with the amount. You can find these credit notes in the tab "Credit notes" on your My plan page. The credit note will automatically be applied to your next invoice.