Rules

6. Choice of Ends & Service
The choice of ends and the right to be Server or Receiver in the first game shall be decided by toss. The player winning the toss may choose or require his opponent to choose:-
a. The right to be Server or Receiver, in which case the other player shall choose the end; or
b. The end, in which case the other player shall choose the right to be Server or Receiver.

Case 1. Do players have the right to new choices if the match is postponed or suspended before it has started?
Decision: Yes. The toss stands, but new choices may be made with respect to service and end.

USTA Comment: The toss shall be made before the warm-up. Choices should be made promptly after the toss and are irrevocable, except when the match is postponed or suspended before the start of the match.