If you're looking to cancel or rebook a flight with the new Delta reservation number, there are a few things to keep in mind. First, make sure that your travel dates and departure and arrival airports are correct. If your travel dates or itinerary changes, be sure to update your reservation accordingly. You can also try calling customer service 716.351.6210 if you have any questions about your reservation. Finally, be sure to have your confirmation number handy when you call customer service - you'll need it to cancel or rebook your flight.