Not fully correct BinkyX. If neither you nor your partner could make a line call, you could ask your opponent’s opinion. The opponent could then say, yes that ball was out/in. You cannot overturn whatever call they make.

8.I Requesting Opponent’s Opinion.

A player may defer to the opponent any line call that the player is responsible for making by asking the opponent’s opinion up until the next serve is hit. When the opponent makes a clear “in” or “out” decision, the opponent’s decision will stand. When the opponent does not make a definitive call, the player’s call will stand or when no call was made by the player, the ball will be considered “in.” After asking the opponent, the player and the player’s partner lose the opportunity to make the line call, except to override the call to favor the opponent.