I've planned a trip to Busan and Seoul in a few weeks with the hotels booked and everything with the exception of getting to Seoul from Busan. I am planning to take the KTX train on the Gyeongbu express line to view the country side of Korea to Seoul. The issue is that I have been trying to access the Korail site but unable to connect. I have already contacted their customer service for help but no reply. I will be leaving to Seoul after staying in Busan for 3 days.
If I am still unable to buy the tickets online, I plan to go to the train station in Busan once I land to see if train tickets are still available. Do train tickets of this travel sell out quick? Are there other sites that allow me to buy train tickets for this type of travel or is Korail the only site? I ideally want to take the train to Seoul, and my backup plan is to buy a last minute plane ticket.
Edit: Disclaimer I am just a traveler looking for answers and not promoting Korail in any way.