Triand products offer a free account. If you upgrade from a free to a paying account you'll be charged for your first month when you upgrade.
Once you cancel you won't be charged again, but you are responsible for whatever charges have already been incurred for the current billing period. For example, if your billing cycle is on the 18th of every month, and you cancel on the 24th, you'll still have to pay for the current month, but you won't be charged again after that. In order to treat everyone equally, no exceptions will be made.
You can cancel your account at any time by logging "Cancel my account" under your Profile. Once you are on the 'Cancel my account' page, click the 'Cancel account' link.