Sorry you weren't happy with your paid account! To downgrade your account, please go to 'Settings', 'Billing' and select 'Update Billing Information." From here, please choose 'Manage Subscription' and select the downgrade option. If you are on Advanced, your account will be automatically downgraded to a Pro status or if you are on Pro your account will be switched to Basic.
We are constantly trying to improve Shift and would love to hear your feedback. Please feel free to share your thoughts with our team by taking our brief feedback survey here.