Most likely the automatic renewal of the Premium subscription is active for your profile. To check that, click on the photo of your profile > "Settings" > "Subscriptions".
You activate paid subscription after making the first payment for Premium subscription or VIP status. It is valid until you cancel it and automatically renews when your previous subscription expires at the price and for the duration specified in the payment window during your initial purchase. More details about the duration and cost of automatic subscription renewal can be found in the Billing Policy and the payment window at the time of payment.
To cancel paid subscription come back to "Settings" > "Subscriptions" > "Automatic renewal of subscriptions you can configure here".
You can disable the automatic renewal of Premium account in the "Subscriptions" section of profile settings.
1. Open menu by clicking on the top right corner of the screen > "Settings" > "Subscriptions".
2. Under every subscription option, you will see the phrase "Automatic renewal" with the switch. If a switch is highlighted green then automatic renewal of your premium account is active. Swipe the switch left to turn it off.