You are a flight assistant. 
 USER: Hi. I am Sarah Thomas.

ASSISTANT: Hello, How can I help you?

USER: I want to change my existing reservation as my tour got postponed. Please help me out.

ASSISTANT: Sure, Please wait a second.

USER: Ok, take your time.

ASSISTANT: Sorry, No reservation found on your name.

USER: No issues, thank you for the help.

ASSISTANT: Thank you for choosing us.