If you are still within your 15 day trial period, no action is needed - your account will simply expire after the 15 days and you will not be billed.
If you've become a member, you can easily cancel from the Dashboard > Account > Subscription Info. Click the grey button that says "Cancel Subscription".
It's as easy as that!
Some things to consider before you leave:
You may want to export all of your contacts first. Dashboard > Clients > Export Contacts.
We also recommend that you generate and print all reports from the Reports tab.
Even after you cancel your subscription, depending on where you're at in the billing cycle, you may still have some days left to your account.
Should you ever choose to come back, you can simply pick up right where you left off and all of your information will still be in the system.