When your no-cost trial ends, you will automatically be charged for a continued premium pass subscription unless you cancel automatic renewal at least 24 hours before the no-cost trial period ends.
How to check the no-cost trial period
Please see How do I check my subscription status?
If you no longer want to continue your subscription
If you cancel at least 24 hours before the end of the no-cost trial period, the automatic renewal will be canceled and you will not be charged.