At this time there is unfortunately no way to change the price of an active membership. This is, however, a function that we are working on introducing in the near future.
For the time being, in order to change the price of your membership, you will first have to cancel it and then re-apply for the membership with a new price of your choosing.
You can do this by going to My Account > Settings > Memberships, then click the "Edit" button on the membership in question.
