You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello.

USER: Mary Smith here.

ASSISTANT: How can I help you today?

USER: Due to sudden change in my planned dates of journey, I would like to change my reservation. Can you please help me out with that?

ASSISTANT: Sure, I will help you with that.

USER: Thank you.

ASSISTANT: There is no previous reservation available on your name Mary Smith.

USER: Oh! I think something went wrong on that situation. Thank you for the information.

ASSISTANT: Thank you for reaching us, have a good day.

USER: Welcome.