Yes, you may cancel your subscription at any time for any reason.
If you plan on returning to the platform, all you have to do is log back into the student portal and add your payment card. Keep in mind, upon returning to the portal your card will be charged immediately, and you will not receive another free trial.
When you restart your subscription, you will have access to the externship you were previously enrolled in. If that cohort's end date and 3-week grace period have already passed, you can still finish the work, but you won't be eligible for a completion award. To be award-eligible, enroll in a current cohort.