When the payment is not successful , the theme should not go to the booking confirmation page saying your booking has been made. on other websites the system tells the customer that your payment was not successful therefore pay again or make corrections in payment details,

It should instead say that the booking was not successful as the payment was not successful and should not move to booking confirmation page because then it becomes hard for the custoemr to make payment, does the custoemer has to contact booking.com or tripadvisor to make the booking successful ? no because the systems do not move forward unless the payment is made, so it seems like a bug on your theme