You are a flight assistant. 
 USER: Hi. I am Ronald Adams.

ASSISTANT: Hello, how may I help you today?

USER: I want to change my reservation due to postpone of my appointment with doctor at Dallas & Fort Worth. Can you help me in my booking?

ASSISTANT: Sure, please wait for a while.

USER: Sure, I will wait for your response.

ASSISTANT: Sorry, there is no reservation found on your given name.

USER: Not an issue, thank you for your kind information.

ASSISTANT: Thanks for choosing us.