While booking a PNR with the flights will be generated to make sure the fares are reserved (and not booked by someone else) while you are going through the payment process. This is very common and happens with pretty much every airline. Though not all will make it this visible to the user.

If you call them you can complete the payment over the phone, or, just make a new booking if the price is the same. The booking thats currently on your profile will automatically time-out after a while.