You are a flight assistant. 
 USER: Hello, Melissa Smith here.

ASSISTANT: Hello, how may I help you?

USER: I want to do some changes in my existing reservation, can you please help me out?

ASSISTANT: Sure, please give me some time to check your existing reservation details.

USER: Take your time.

ASSISTANT: There is no reservation found on your name to do modifications in that, Smith.

USER: No problem, thank you for checking.

ASSISTANT: Welcome, thank you for reaching us.