I signed up on the Lingokids website
Please remember that uninstalling the app doesn’t cancel a subscription automatically.
I'm reading this in a device with Lingokids installed and logged in with my account:
You can cancel your subscription directly in the app by managing your subscription here.
I'm reading this in another device or on the computer (web browser):
Please note that you can cancel your subscription in the app following these steps.
Afterward, the subscription will be canceled at the end of the current billing cycle.
Have you uninstalled the app or don’t remember what e-mail address you registered with?
Searching in your email inboxes, you will find a subscription confirmation email from Lingokids and payment receipts; your membership was registered with that email account.
If you're having trouble canceling, or would like to request a refund, please reach out to us at the Help 
widget on the lower right corner.