Payments are managed by Stripe Checkout (https://stripe.com/checkout) and are 100% secure.
During the 7 day free trial, you don't need to enter any crdit card information. When the free trial ends, your number will be kept by Ottspott until the last day of the month. During this period you can still pick a plan and enter your payment information.
In the Ottspott back-office, please go to the "Billing" section and pick the plan. If you have a promo code, you can enter it in this section as well.