Placeit has subscription models and the option to buy a single design as well. If you have an existing subscription, it will be auto-renewed based on the payment details on record if you do not alert on the cancellation to placeit. You have to intimate the team at least 1 day before the billing cycle ends so that they can process it. Placeit does not entertain refund requests in general however you can write to them at hi@placeit.net if you want a refund.