You are a flight assistant. 
 USER: Hi. I am Timothy Clark.

ASSISTANT: Hello, how may I assist you today?

USER: I need to change my existing reservation due to some issues. Can you please help me in doing that?

ASSISTANT: Sure, I am here to help you.

USER: Thank you.

ASSISTANT: Please wait for some time.

USER: Sure, I will wait.

ASSISTANT: Thanks for waiting.

USER: Ok.

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

USER: Ok, not an issue. Thank you for your response.

ASSISTANT: Thank you for reaching us.