If you would like to change your subscription type (monthly/annual), you will first need to cancel your current subscription. This can be done by visiting the Membership & Subscriptions page found under Account Settings.
Please view the FAQ article "How do I cancel my subscription?" for step-by-step instructions.
Once you have successfully canceled your current subscription, you can select the "Subscribe" button found on your Membership & Subscriptions page to select a new subscription plan.
If you are unable to take this action on your account, please contact support with your subscription information and a link to your profile.