Trying to make a Can't Move script but the script doesn't work? This title is specific

Hello, I'm trying to make a character customization and I have a problem, I want to make the player not move when the GUI is displayed and can move if the GUI is not displayed.

I tried this:

local plr = game.Players.LocalPlayer
local char = plr.Character

while script.Parent.Parent == plr.PlayerGui do
	char:FindFirstChild("UpperTorso").Anchored = true
end

while not script.Parent.Parent == plr.PlayerGui do
	char:FindFirstChild("UpperTorso").Anchored = false
end

And this:

local plr = game.Players.LocalPlayer
local plrname = game.Players.LocalPlayer.Name
local char = game.Workspace:FindFirstChild(plrname)

while script.Parent.Parent == plr.PlayerGui do
	char:FindFirstChild("UpperTorso").Anchored = true
end

while not script.Parent.Parent == plr.PlayerGui do
	char:FindFirstChild("UpperTorso").Anchored = false
end

Nothing worked, By the way I tried doing if ... then, Except of the while ... do and I'm using it in a LocalScript

Thanks, MajinBluee

game.Players.LocalPlayer.PlayerScripts.ControlScript.Disabled = true

So add WaitForChild() function to wait until the character is in workspace Seeing this code it will not work with Filtered enabled since you are anchoring a the torso in the local script it will only be achored on client game and not on server

Read more on how to make it Filtered enabled https://wiki.roblox.com/index.php?title=Remote_Functions_%26_Events

local plr = game.Players.LocalPlayer
local plrname = game.Players.LocalPlayer.Name
local char = game.Workspace:WaitForChild(plrname)

--Added it all in one while since the program will never have reached the second while
while true do
	if script.Parent.Parent == plr.PlayerGui then
		 char:FindFirstChild("UpperTorso").Anchored = true
	else
		char:FindFirstChild("UpperTorso").Anchored = false
	end	
	wait(0.5)
end

Now there is a better way to do this instead of checking every 0.5 seconds if the player has gui. This is too much process intensive I think.

You could also try this:

-- Place script inside of the gui. Also make sure that the script is a local script

local toggle = false
local Humanoid = game.Players.LocalPlayer.Character:FindFirstChild("Humanoid")

script.Parent.TextButton.MouseButton1Click:Connect(function()
	if toggle == false then
		toggle = true
		script.Parent.Frame.Visible = true
		Humanoid.WalkSpeed = 0
	else
		Humanoid.WalkSpeed = 16
		script.Parent.Frame.Visible = false
		toggle = false
	end
end)