You are a flight assistant. 
 USER: Hi, I am Alexander Lopez.

ASSISTANT: Hello, how may I help you?

USER: As my plan to visit my grandmother's home got postponed, can you help me in changing my existing reservation?

ASSISTANT: Sure, please wait for a while.

USER: Ok, take your own time.

ASSISTANT: Sorry to inform that there is no reservation found with your name.

USER: That's ok, thank you for the response.

ASSISTANT: Thank you.