How to cancel magazine subscription in iPad?

I just purchase GQ iPad app, I immediately purchased the $1.99 1 month subscription because it's cheaper than buying it with $4.99.

However, after carefully reading the description of GQ from iTunes. It says that it will automatically renew ended subscriptions unless cancelled or turned off.

So, I logged in to my account from the GQ app but there is no option to cancel the subscription.

Does anyone know a way to cancel my subscription? Or upgrade it to an annual subscription?