You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello. How may I guide you today?

USER: I want to change my existing reservation due to some problems, can you please help me in this?

ASSISTANT: Sure, I will help you with that. Please give me a minute.

USER: Thank you. Sure, I will wait.

ASSISTANT: may I know your name please?

USER: Sure, my name is Carol Wright.

ASSISTANT: I am sorry to say that there is no reservation found.

USER: Ok, that's fine.

ASSISTANT: Thank you for contacting us.

USER: Thank you for your service.