[RyDeR`]

You have to define them as strings not integers.
That will output: ►

pawn Код:

new
    title[64],
    info[256]
;
if(sscanf(params, "s[64]s[256]", title, info)) return SendClientMessage(playerid, RED, "/mess [title] [info]");
return ShowPlyerDialog(playerid, 899, DIALOG_STYLE_MSGBOX, title, info,"OK","OK");

This should work.