In order to change your billing cycle, please visit https://web.descript.com/subscription. If you have more than one drive, be sure to choose the appropriate drive to modify by clicking on the dropdown selector in the top-left corner.
Next, click the Edit button on the right side of the "Subscription" row.
Here you will be able to change the "Billing Cycle" option to Annual then click Update.
Once completed, your billing cycle change will occur at the start of the next billing cycle.