If you don't see a cancel option,
You might have subscribed to premium through the iPhone or iPad app.
To cancel your subscription, you need to cancel it from iTunes. Your subscription is being handled by Apple.
Information on how to do this can be found here:
Contact support if you still need help:
If you get an automated reply email telling you to check the help section or the community, you need to reply back to it.
Support usually replies within 24-48 hours.