I signed up for a 14 day free trial wit...

Unfortunately, the old saying "There's no free lunch" applies here. They got you to sign up, and now they're hiding the undo option from you.

You could try calling them, there's bound to be a "Contact Us" page on their website. You could also email, or use a contact form if they have one.

When you signed up for the trial, did you use a credit card? If you didn't give them your payment information then you're safe anyway.