Unfortunately we cannot modify one type of membership into another one.
The best thing you can do is to cancel your membership. After its expiration you can choose a new form of membership in your profile settings. A new verification of the transaction is required.
In your profile settings you can choose a new membership.
On the page where you can choose your membership you can choose another form of membership.
In case you still have questions, please contact our customer service through the envelope button!