For both the free trial and paid Unlimited subscription, it is easy to cancel at any time to avoid any future charges.
If you do not wish to have the free trial auto-renew into the paid subscription after 30 days or you want to cancel your paid Unlimited subscription, simply go in the app under Settings > Plus Unlimited > Manage Subscription > Cancel Automatic Renewal. See screenshots below.
Once cancelled you will be able to use your subscription up until your renewal date. In other words, if your renewal date was March 1, 2016 and you cancelled on February 15, 2016, then you would be able to use the remainder of your subscription until 3/1/2016 because all of February was already part of your free trial (or already purchased if you were on the paid plan). On 3/1/2016 your card would not be charged for your subscription fee and you would no longer be an Unlimited subscriber. At this point you would no longer be eligible for a free trial in the future, but you would still be able to sign up for a regular paid Unlimited subscription any time.
You can always start your subscription again by going in the app under Settings > Plus Unlimited > Renew Subscription. See screenshot below.
Learn more at: postmates.com/plus-unlimited