You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello. How can I assist you today?

USER: Actually, I want to change my existing reservation which is done recently due to some problems, can you please help me in this?

ASSISTANT: Sure, may I know your name to check for the previous reservation?

USER: Sure, my name is William Turner.

ASSISTANT: I found your reservation. Can you please help me with the airport codes?

USER: Sure, my respective airport codes are from IAH to LAX.

ASSISTANT: Could you please share your travel dates?

USER: Ok, my planned dates of journey are from Nov, 14 to Nov, 16.

ASSISTANT: Do you have any class preference?

USER: I am comfortable with any class preference.

ASSISTANT: May I know your connection limit?

USER: Yes, I need a single connecting flight to travel.

ASSISTANT: Do you have any other specification that you are looking for?

USER: Not required.

ASSISTANT: Do you have airline preference?

USER: I am ok with any airline preference.

ASSISTANT: William Turner, I am sorry to inform you that there is no flight available at your request.

USER: Ok, no problem. Anyways, thank you for your service.

ASSISTANT: Thank you for contacting us.