Yes, you can change the type of Plus subscription you have.
If you made the purchase from the website or an Android device
If you have purchased a monthly subscription, you can switch to the yearly subscription, which will become effective at the end of the month for which you have already paid. To do this, just click on the "Upgrade to yearly Plus" button in the Subscriptions section of your account from the website.
Or if you have purchased your subscription using an Android device, you can also manage it directly from the app.
To do so, tap on Manage subscription in the Domestika Plus section:
From here you can change your monthly subscription and upgrade to yearly.
If you have purchased a yearly subscription, you will have to wait until the end of the current period before you can switch to the monthly plan. You can cancel your yearly plan from the Subscriptions section on the web and from Manage subscription on the app. At the end of the period, purchase the monthly plan. Don't worry - even if you decide to cancel your yearly subscription, you will still enjoy the Plus benefits until the end of the period which you have already paid for.
If you purchased the subscription from an iOS device
If you subscribed to Plus using an iOS device, as renewal payments are processed directly by the Apple Store, when you tap on Manage subscription you will be redirected to the subscription section of your Apple ID, where you will be able to manage your Plus subscription or cancel the renewal if you wish to do so. You can find more information on how to manage your Apple subscriptions here.
Other articles that may interest you: