Came to say the same. Except it is the team captain that you should address.

Typically they will then escalate to the coach/club coordinator or something. By the time that is finished the guilty party has either left by their own volition already or through the other spectators.

Volleyball is a chill sport and I have had only once in refereeing junior games (<16/18) that a spectator went to far.

Most shenanigans if any is typically directed at the referees not even the players.

There has been a slight uptake in nastiness that I attribute to the sport becoming more popular.

(Context: the Netherlands, 12 years of experience from the lowest classes to 2nd division)