Collision groups not disabling collision?

I have look at it many times and I can't figure out what's wrong, I have NPC's that walk around and I don't want collision with other NPS's or players

Script code:

local phys = game:GetService("PhysicsService")

local npcGroup = "NPC"
local plrg = "Player"

phys:CreateCollisionGroup(npcGroup)
phys:CreateCollisionGroup(plrg)

phys:CollisionGroupSetCollidable(plrg, npcGroup, false)
phys:CollisionGroupSetCollidable(npcGroup, npcGroup, false)
phys:CollisionGroupSetCollidable(plrg, plrg, false)


game.Players.PlayerAdded:Connect(function(plr)
    plr.CharacterAdded:Connect(function(char)
        for i =1,#char:GetChildren() do
            if char:GetChildren()[i]:IsA("Part") or char:GetChildren()[i]:IsA("MeshPart") then
                phys:SetPartCollisionGroup(char:GetChildren()[i],plrg)
            end
        end

    end)
end)

NPC Code:

local phys = game:GetService("PhysicsService")
for i=1,#script.Parent:GetChildren() do
    if script.Parent:GetChildren()[i]:IsA("Part") then
        phys:SetPartCollisionGroup(script.Parent:GetChildren()[i],"NPC")
    end
end