Absolutely! You can change your plan yourself in your 'Account.' Then select the 'Billing' tab.
You can review the various options under each plan, compare the monthly vs annual plans and simply click the 'Change Plan' button to make the change.
We'll prorate the amount at the beginning of the next billing cycle.
If a plan is not available there will be a reason at the bottom of the plan description indicating what features you are currently using that are not supported on that specific plan.