Your subscription is managed by Google. So to cancel it, you have to use their interface directly (https://play.google.com/store/account) or via your device:
- Click on
- Me (at the bottom of the page)
- Parameter button (top right)
- The subscription
- Manage my subscription
You will then be directed to your Google Play account.
- Scroll down the menu at the top left
- Click on "Account".
- Click on "Subscription" then "Cancel" the Petit BamBou subscription
- or otherwise, you can also do it from their website https://play.google.com/store/account.
If your subscription does not appear, it means that you have not subscribed via the app.