AirBrush offers a free trial period of the premium subscription, which is only available under below the three circumstances:
1. You have not used the trial chance before.
2. You selected the auto-renewable yearly subscription.
3. You have enabled the 'Free trial' option while purchasing.
If you initiated it but do not want to renew the subscription, please cancel your subscription at least 24 hours before the end of the trial. Otherwise, the App Store or Google Play Store will automatically deduct a subscription fee from your account or associated credit card. This information is also shown to you in the pop-up message from the App Store/Play Store when you subscribe.
After you have used your free trial, there will not be a free trial offered the next time you try to subscribe and you will be charged immediately.