Are you sure you made a premium account? If you did, you would be asked to pay and your top menu should say "Premium user (プレミアム会員)" like this http://i56.tinypic.com/16c52lj.png
If that is the case, if you want to cancel If you paid through webmoney and do 3-month subscriptions, if you stop paying your account fees, once your subscription runs out, you will be back to non-prem. There's probably a way to cancel right away, but I don't know of it and you probably wouldn't be refunded for the money you paid for the subscription.
If you're on monthly auto-pay (i.e. through Paypal), turning off the auto-pay function will instantly turn your account back to non-prem.
no subject
If that is the case, if you want to cancel
If you paid through webmoney and do 3-month subscriptions, if you stop paying your account fees, once your subscription runs out, you will be back to non-prem. There's probably a way to cancel right away, but I don't know of it and you probably wouldn't be refunded for the money you paid for the subscription.
If you're on monthly auto-pay (i.e. through Paypal), turning off the auto-pay function will instantly turn your account back to non-prem.