You can cancel it yourself, in a couple of minutes, from the web — no need to go through the app:
Go to client-pomospeak.personalized.app and log in with your account email and password.
On the Account overview page, find Your subscriptions and tap Cancel subscription.
Select a reason when prompted, and you're done.
Your subscription stays active until the end of your current billing period — cancelling doesn't cut off access right away.
If you subscribed through the App Store or Google Play instead, cancel there — Apple and Google manage the billing for those subscriptions directly:
App Store: Settings > [Your Name] > Subscriptions > PomoSpeak > Cancel Subscription.
Google Play: Play Store app > Menu > Subscriptions > PomoSpeak > Cancel.