You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello.

USER: My name is Melissa Gonzalez.

ASSISTANT: Melissa, how can I aid you?

USER: I want to change my existing reservation, can you help me?

ASSISTANT: Sure, I am here to help you. Let me check your reservation status.

USER: Sure, I will wait for your reply.

ASSISTANT: Melissa, I did not find any reservation under your name.

USER: It's fine, not an issue. Thank you so much.

ASSISTANT: You are welcome and have a nice day.