Hello, dear Nat B.
Due to the circumstances it should be clarified that we are online-agency and the payment security is very important to us. In this regard we take all the measures to protect our customers from the potential threats. If the payment security system generates a request for confirmation of the legitimacy of credit card usage, we are obliged to make the appropriate verification and make sure that the purchase of services had been authorized by the cardholder. Of course, we are interested in selling the products, but taking care of our customers and providing them with a safe usage of our resource is a priority of our work.
The detailed information about the standards of payment security and anti-fraud payment verification, which are used by our resource, you are able to review at our website in the section "Legal Information". To do this you may use the following link:
https://avia.kissandfly.com/content/antifraud-verification.html
Hope that this information will be useful for you.

Don't book. Use a reputable site. They are scammers.