When you subscribe for a Premium Subscription via the app, you are on a monthly subscription. If you want to upgrade to an annual subscription via app unfortunately it is not possible as we do not offer annual subscription directly via in-app purchases.
In order to accommodate your annual upgrade request, you will first need to cancel your monthly subscription via the app store and then resubscribe to the annual subscription via our website.
To cancel your currently monthly subscription, please follow these steps - https://support.apple.com/en-us/HT202039
Once you have cancelled your monthly subscription and your Premium subscription expires, you can re-subscribe to the annual subscription on our website by clicking here - https://seekingalpha.com/checkout?service_id=proresearch
Customer support service by UserEcho