How to cancel Norton 360 Pay-Trial subscription? Want Norton Internet Security 2010 instead

I used my credit card to sign up for a 30 day trial of Norton 360, but would like to just go with Norton Internet security 2010 instead.  Where do I go to cancel?  I logged into my account and it just gives me the option to buy a registration key even though I already have one.  I’m confused.  Any help would be appreciated.  Thanks!