You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello. How could I aid you today?

USER: I want to change my existing reservation which is done recently due to some problems, can you please help me out?

ASSISTANT: Can I know your name please?

USER: Sure, my name is Charles Collins.

ASSISTANT: Please give me a moment.

USER: Sure, I will wait.

ASSISTANT: There is no reservation found with your given name.

USER: Ok, no problem.

ASSISTANT: Thank you.

USER: Anyways, thank you for your service.