Why won't this finding of a username work?

I have a feeling I screwed up on Line 3 at the end. Can someone help me edit it? Thanks :)

game.Players.PlayerAdded:connect(function(player)
	Username = player.name
	game.Players.LocalPlayer.PlayerGui.PhoneGUI.Menu.Owner.Text = (Username)
end)

Let's look at two scenarios.

1.) Using a local script

2.) Using a regular script

One issue with your code is that you can't use LocalPlayer and .PlayerAdded in the same script due to the simple fact that one only works in server-scripts and one only works in localscripts.

If this is a localscript, we can make the code to:

local plr = game.Players.LocalPlayer;
local name = plr.Name;
repeat until plr.ChildAdded:wait().Name == "PlayerGui"
plr.PlayerGui.PhoneGui.Menu.Owner.Text = name;

In a regular script, we can do the following:

game.Players.PlayerAdded:connect(function(plr)
local name = plr.Name;
plr.PlayerGui.PhoneGui.Menu.Owner.Text = name;
end)