As longs as the billing is current on your site you can cancel at anytime.
There should be a couple options on your end.
1. Go into your site admin and locate site settings -> billing settings
2. Depending on the account you might need to cancel within your partner portal -> client -> details -> delete site
Hope this helps!
Humm...In looking under your ID and site I see you have only trial sites which I can remove for you.
However you said you are paying for a site which site would this be? I notice "balletsample.businesscatalyst.com" is under trial and is already "expired".
The other trial site are as follows under your account.
Which site would you like me to delete?
Maybe I have another username/password. Here's the bill I'm referring to.
You do not need to pay this invoice. Your CreditCard will be charged automatically on 03-May-2012.
03-May-2012 Invoice Number
I see now the site in question.
You can access your portal below...
Then locate the "client" tab and go to details -> delete/cancel site as required.
Europe, Middle East and Africa