We cannot change the date, time or party size of a booking on the site. There is no edit button, and adding one that quietly cancelled and rebooked would be worse than not having one.
Write to us with the booking reference and what you want changed, and we will ask the operator.
Ask before you cancel, not after
Often the operator's answer is to cancel and rebook. That is subject to their cancellation terms like anything else, so if you cancel first and the answer turns out to be no refund, you have lost the booking and the money and gained nothing.
Asking first costs you nothing and keeps the booking intact while we find out.
Adding people
Usually a second booking for the extra places is simpler and safer than amending the first, because it does not put the existing places back on sale. Check availability for the same date and time before you cancel anything.