You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello, how can I serve you?

USER: I want to change my trip dates of my existing reservation as my plan to go for shopping at Houston got postponed. Can you help me in changing the reservation mad on name Nancy Lopez?

ASSISTANT: Sure, please wait a moment I will check and let you know.

USER: Sure.

ASSISTANT: Sorry, no reservation found on your name.

USER: It's Ok. Thanks for your assistance.

ASSISTANT: Thank you for reaching us.