Can tennis server call his own serve out?

Answer 1

In professional tennis, there are line judges for that.

In non-professional tennis, however, a server can call his or her own serve out. Most do not because it is a point against them, even though the opponent thought the serve was in.

Answer 2

It is the obligation of a server to announce the game score prior to the start of each point In a game during an unofficiated tennis match. The server normally announces his or her score before announcing the score of the receiver. The game count is announced by the server prior to the start of the first point of a new game. The set score is announced by the server prior to the the start of the first point in the first game of each new set. The server can discuss these scores with the receiver and the receiver can dispute the scores. It is up to the server to call the score correctly. The announcement of the score as made by the server after each point of a game is supposed to be final. Any dispute should be taken up with the persons in charge during tournament play.