We purchased two Business Class tickets on August 27, 2019. Due to EU pandemic travel restriction in 2020 and 2021, we called the Turkish Airlines customer service several times. These two tickets hence became open tickets valid until 12/31/2021 as we were told from Turkish Airlines Zero Change Fee and Change to Open Ticket policies for international flights on Turkish Airlines website (we have screenshots to prove it). On February 2, 2021, we called the Turkish Airlines customer services. Their call center changed our open tickets to September 2 (LAX to IST) and September 14 (from IST to LAX). Since then, we have received Turkish Airlines email correspondences about flight schedule changes and last on 8/31/2021, an email to remind us applying Turkey visa. On Sep. 2, 2021, the date of travel, Turkish Airlines LAX check-in and ticketing team surprised us of the expiry of our tickets as of 6/30/2021 for the first time on the date of travel, which is completely unacceptable. We were told by their ticketing agents that the online booking and phone customer service systems, which had been verifying up until 9/2/2021 that we had valid tickets, does not sync with the LAX-specific ticketing check-in system. Finally, they refused to issue boarding passes to us, and forced us to purchase new tickets with no other options and no transparency. They told us that if we wanted to fly on 9/2/2021, we had to purchase completely new tickets. We were forced to purchase two new much more expensive full price business class tickets with only 1 hour to boarding. Turkish Airlines never notified us PRIOR to 9/2/2021 that our tickets were expiring through any written email, screenshotted or documented proof. Turkish Airlines unilaterally voided our valid tickets and claimed they were expired on June 30, 2021. These specific instances violate the U.S. Code of Federal Regulations 14 CFR 399.4 Rule under 49 U.S.C. 41714, 40113(a). We are aware that we are protected under federal consumer protection laws and regulations, and based on our experience with Turkish Airlines on 9/2/2021, our consumer rights have been violated.