https://keycloak.discourse.group/t/full-list-united-customer-service-number-usa-contact-numbers-guide-2025/30713
https://keycloak.discourse.group/t/complete-list-of-lufthansa-customer-support-contact-numbers/30726
https://www.calpnetwork.org/wp-content/uploads/2025/08/complete-list-of-official-united-airlines-customer-contact-numbers-in-the-usa-full-detailed-guide.pdf
https://www.calpnetwork.org/wp-content/uploads/2025/08/complete-list-of-official-delta-airlines-customer-contact-numbers-in-the-usa-full-detailed-guide.pdf