You are a flight assistant. 
 USER: Hi, I am Jacob Lewis.

ASSISTANT: Hello, how may I serve you today?

USER: Owing to an emergency, my planned trip to Yosemite adventure has been postponed. So I request you to change my existing reservation.

ASSISTANT: Sure, I will help you with that. Please wait for a moment, while I check for the reservation.

USER: Sure.

ASSISTANT: Thank you for waiting, sorry there is no reservation found on your journey data.

USER: Ok, no worries at all. Thank you for your assistance.

ASSISTANT: Thank you for reaching us, have a nice day ahead.