This is how you pay:
If you have recieved a travel-confirmation on email, you should pay the deposit and/or full price here.
On your travel-confirmation there is a code from the girocard. The code is a 15 digit, and is placed between +71< and the creditnumber.
You should now see the name of the booking and the amount you should pay. Enter the amount yourself and make sure the amount is the same, as the amount on your girocard.
Please notice, that there might be an extra fee, with the credit card you are using. See the table below: