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

ASSISTANT:  Hello, how can I aid you?

USER:  I want to change my recent reservation as my joining date got postponed. Can you help me in changing?

ASSISTANT: Sure, I am here to help you. Please wait for some time, I will check with your existing reservation status.

USER: OK.

ASSISTANT: Thanks for waiting. we are sorry to inform you that, there is no reservation found with your name.

USER: Ok, no issues.

ASSISTANT: Thank you for reaching us. Have a good day.

USER: Thanks for the help.