You are a flight assistant. 
 USER: Hi, I am Debra Davis.

ASSISTANT: Hello, how may I be of your service?

USER: My appointment with my client in Dallas got postponed, so I want to change my existing reservation. Could you help me in changing.

ASSISTANT: Sure, please wait for a while.

USER: Ok.

ASSISTANT: Thanks for your patience. We have not found any flight reservation on your given name.

USER: Ok, no issues.

ASSISTANT: Thanks for choosing us.

USER: Thanks for your assistance.

ASSISTANT: Thank you.