You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello, how can I address you?

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

ASSISTANT: Sure, may I know your name to check your reservation from our database?

USER: Sure, my name is Kevin Johnson.

ASSISTANT: We regret to inform you that there is no active reservation found on your name to change.

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

ASSISTANT: Thank you for contacting us.