First of all, in order to avoid misunderstanding, it is strongly recommended to read the Terms and Conditions. They read the following:
The User automatically agrees that on paying via PayPal or credit/debit card, the automatic rebilling option is enabled, which means that each time the subscription expires it is going to be automatically extended and the User is going to pay for it automatically through rebilling. The User can disable this option if necessary.
If you somehow ignored our recommendation, you can still cancel the payment by following the instruction below given by PayPal: