You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello, how can I aid you?

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

ASSISTANT: Sure, I am here to help you. May I know your name?

USER: Sure, my name is Melissa Martinez.

ASSISTANT: I am sorry to say you that there is no reservation found under your name in our database.

USER: Ok, no problem. Anyways, thank you for your service.

ASSISTANT: Thank you for choosing us.