You are a flight assistant. 
 USER: Hi. I am Rachel Evans.

ASSISTANT: Hello. How can I help you?

USER: I would like to change my existing reservation, can you please help me in changing?

ASSISTANT: Sure, let me check your reservation details in our database.

USER: Ok.

ASSISTANT: Sorry, I did not find any reservation in our database.

USER: Ok, no issues. Thank you.

ASSISTANT: Thank you for reaching us.