My Partner Yelled, “OUT.” The Ball Then Landed In and My Partner Yelled, “No, it’s IN.” The Opposing Team Said You Called It Out.

Well, as confusing as it may be, this happens all the time. Let me read what the rule book states:

6.D.11. While the ball is in the air, if a player yells “out,” “no,”
“bounce it,” or any other words to communicate to
their partner that the ball may be out, it shall be
considered player communication only and not
considered a line call.
6.D.12. An “out” call made after the ball bounces is a line call.
The ball is dead and play shall stop. If, upon appeal,
the referee overrules any type of “out” call, it is a fault
against the player or team that made the “out” call.
Exception: If the match has line judges, the baseline
and sideline judges are responsible for the call. (See
Rule 13.E.2)

NOTE: we also mention this in a previous post from last year, further down in the posts.