New subscribers to either KAYA PRO tier get a 3 day free trial. Your exact trial end date and next billing date are managed by your app store rather than by KAYA directly, you can find this in the "Subscriptions" section of your iOS or Android app store account.
KAYA PRO refunds are not guaranteed once a payment is made, so if you plan to cancel, do it before your 3 day trial ends so you are not charged for the full subscription. If you are charged and want to request a refund, see "Can I get a refund for a KAYA purchase" for the current steps for iOS and Android.