You can choose to enable or disable automatic payments at any time from within the Snap app.
When enabled, the monthly subscription fee will automatically be charged to your credit card at the beginning of each 30-day billing cycle. You will be notified via email about the upcoming charge a few days before the payment is due as well on the day when the payment is actually charged to your card.
If you disable automatic payments, your current paid cloud storage plan will continue until the end of the billing cycle, at which point your paid plan will expire. Your Snap will then automatically be reverted to the free 1-day plan.