Please note that by ordering your free box, you are signing up for regular recurring deliveries. However, you can cancel at anytime easily online by signing into your account. Cancel before the second box ships and you won’t be charged anything.
Tip: When deals like this come up and require enrolling in a subscription program, I always add an event in my calendar on my phone with the customer service number and set the reminder for a few days before the last day to cancel. This allows me to try deals without worry of forgetting to cancel!