If you are a Premium User, and realize you don’t need the Premium features provided by Exirio, you can always downgrade your subscription to Starter (free).
In order to do that, navigate to your Settings page, and then to "Subscription portal" (if you first upgrade from the web or with an Android device).
You will be redirected to your billing page with Stripe, where you can amend or cancel your Premium subscription.
If you upgraded on iOS, you can manage your Exirio subscription in the Settings page of your Apple device - as you already do for all other subscriptions.