https://unitedhelp.helpshift.com/hc/faq/34-ways-to-hold-delta-airlines-customer-service-by-phone-email-or-chat-a-full-comprehensive-guide
https://unitedhelp.helpshift.com/hc/faq/34-ways-to-hold-delta-airlines-customer-service-by-phone-email-or-chat-a-full-comprehensive-guide