https://vpuniverse.com/forums/topic/12569-ways-to-reach-frontier-airlines-customer-service-by-phone-number-chat-and-emails-options-a-step-by-step-full-guide/
https://vpuniverse.com/forums/topic/12582-55-ways-to-contact-frontier-airlines-customer-service-by-phone-number-chat-and-email-direct-methods-explained/
https://www.chilecomparte.cl/foros/topic/4889092-55-ways-to-call-frontier-airlines-customer-service-via-phone-email-or-chat-options-a-step-by-step-extended-guide/
https://www.chilecomparte.cl/foros/topic/4889099-ways-to-contact-travelocity-customer-service-via-phone-email-or-messaging-travel-made-easy/
https://vpuniverse.com/forums/topic/12695-how-to-connect-with-united-airlines-customer-service-using-phone-or-online-chat-a-full-help-guide/