Yes, you can switch plans at any time.
If you are on a Basic plan, and want to upgrade to Pro+, simply head to your Settings on the dashboard, select Plan Info, and then click Upgrade.
Monthly Pro+ plan users can switch to an Annual plan and save 50% on their payment plan. See our pricing plans here.
If you are already an Annual Pro+ user, you will need to cancel your subscription and wait until the subscription is up before you can switch to a monthly plan. You may also contact our support at firstname.lastname@example.org to help you with your request.