I use command " /lp user InfinCZ addprefix 10 "&c[testing]" ".
And in chat doesn't show prefix [testing].
When I try this command again show message " infincz already has that prefix set. ".

And I use command " /lp user InfinCZ info " and show Current Prefix: "[testing] " .
Thanks,

Infin

Sponge or Spigot?
What chat plugin are you using?

Spigot, but all is ok.
I download plugin Ultra chat ---> https://www.spigotmc.org/resources/ultra-chat.13776/ .
And all is work.

Thanks,

Infin

But how I replace current prefix ?

/lp user/group <name> meta addprefix <weight> "<prefix>"
@lucko might be able to answer this better than I can, though.

Ok and how i change priority?

Weight is priority.

Weight - this is just a number which determines the priority of the prefix/suffix. A higher number = a higher weight and a higher priority.