Lead with the reference
Start your message with the transfer booking reference and passenger name. Then give the old flight and the replacement flight. This makes it clear that you are updating an existing journey rather than requesting a second pickup.
Include the arrival day
Send the revised local arrival date and time together. A change across midnight can shift the pickup to another day. If the airline has not confirmed a replacement, say so instead of providing a guessed arrival time.
Wait for the revised arrangement
Ask for confirmation of the new pickup plan and any applicable price or waiting conditions. Flight information by itself does not settle all booking changes. Keep the revised confirmation with your travel documents.
