Click the Abandon This Plan button underneath the Trainer's picture
Confirm Abandon when the pop-up box appears
From here, the plan will be removed from the phone. If you haven't attached any activities to the plan, it will be removed from your phone, and the website, and you will be able to select the plan with the same, or a new start date immediately.
If you have attached even a single activity to your Training Plan, it will still remain in your Past Training Plans on the website. It will remain in the current section six months after the end date of the class, which at that point will be moved removed from your profile. You should still be able to sign up for a class, but you will not be able to sign up for the class on the same date as before. If you wish to sign up again, please sign up for another class and then follow the steps here: http://support.runkeeper.com/entries/22063091-how-to-change-your-tr...