Yes, United Airlines provides 24-hour customer care
https://community.dynamics.com/forums/thread/details/?threadid=3c00001b-bce3-ee11-904d-000d3a57434b

The KLM 24-Hour Rule is a customer-friendly policy that allows passengers to make changes or cancel their flight bookings within 24 hours of purchase
https://community.dynamics.com/forums/thread/details/?threadid=4973d06e-a5e3-ee11-904d-000d3a57434b

KLM’s 24-hour rule allows travellers to cancel their reservation within 24 hours for a full refund, provided the booking was made at least 7 days....
https://community.dynamics.com/forums/thread/details/?threadid=86e1b07c-a3e3-ee11-904d-000d3a57434b

KLM’s 24-hour rule allows consumers to cancel a ticket booking for a full refund within 24 hours of purchase, provided the reservation was made at....
https://community.dynamics.com/forums/thread/details/?threadid=33eb78f8-9fe3-ee11-904d-000d3a57434b

KLM’s 24-hour rule allows consumers to cancel a ticket booking for a full refund within 24 hours of purchase, provided the reservation was made at....
https://experience.dynamics.com/ideas/idea/?ideaid=ddc8d0ca-9de3-ee11-a73d-6045bd7ce06d

Yes, 𝓚𝓛𝓜 provides customer service 24-hours for their passengers
https://ideas.powerapps.com/d365community/idea/7fce32ea-38e2-ee11-a73d-000d3a01b6a8

If you need to a Lufthansa representative fast 𝙇𝙪𝙛𝙩𝙝𝙖𝙣𝙨𝙖 𝘼𝙞𝙧𝙡𝙞𝙣𝙚𝙨 for help, you have got a few options. You can call them on their customer....
https://ideas.powerapps.com/d365community/idea/2671a6a0-36e2-ee11-a73d-000d3a01b6a8

How do I talk to a 𝙇𝙪𝙛𝙩𝙝𝙖𝙣𝙨𝙖 𝘼𝙞𝙧𝙡𝙞𝙣𝙚𝙨 representative fast?| @24*7 Help & Support If you need to a 𝙇𝙪𝙛𝙩𝙝𝙖𝙣𝙨𝙖 𝘼𝙞𝙧𝙡𝙞𝙣𝙚𝙨 representative fast
https://ideas.powerapps.com/d365community/idea/96cf9264-35e2-ee11-a73d-000d3a01b6a8

f you need to a Delta representative fast Delta flights for help, you have got a few options. You can call them on their customer....
https://community.cisco.com/t5/wireless/how-do-i-talk-to-a-delta-representative-fast-1-844-604-2944/m-p/5040071#M268181