You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello.

USER: Melissa Carter here.

ASSISTANT: Is there any help that you need from our agency?

USER: Can you change my flight ticket reservation?

ASSISTANT: Sure, I can help you in changing process. Please give me a moment to check it.

USER: Ok, I will wait.

ASSISTANT: Thank you for waiting, there is no reservation found for the user name in our previous reservation list.

USER: Ok, not a problem. Thank you.

ASSISTANT: You are most welcome and thank you for reaching us.