I need help with a custom chat gui?

this is my custom chat gui script it works and everything but the default roblox chat gui still pops up how do I disable the default chat gui?

function UpdateOldLabels(Parent)
    for i,v in pairs(Parent:GetChildren()) do
        if v.Name:sub(1,4):lower() == "line" then
            local LineNumber = v.Name:sub(5)
            if LineNumber == "12" then
                v:Destroy()
            else
                v.Name = "line"..tostring(tonumber(LineNumber) + 1)
                v.Position = v.Position - UDim2.new(0,0,0,15)
            end
        end
    end
end

game:GetService("Players").PlayerAdded:connect(function(player)
    player.Chatted:connect(function(msg)
        for _,v in ipairs(game:GetService("Players"):GetChildren()) do
            UpdateOldLabels(v:WaitForChild("PlayerGui").ScreenGui.Frame)
            newchatline = Instance.new("TextLabel",v:WaitForChild("PlayerGui").ScreenGui.Frame)
            newchatline.Text = player.Name.. ": " ..msg
            newchatline.Size = UDim2.new(1,0,0,15)
            newchatline.Position = UDim2.new(0,0,1,-15)
            newchatline.Font = "SourceSansBold"
            newchatline.TextColor3 = Color3.new(1,1,1)
            newchatline.TextStrokeTransparency = 0
            newchatline.BackgroundTransparency = 0.5
            newchatline.BorderSizePixel = 0
            newchatline.FontSize = "Size14"
            newchatline.TextXAlignment = "Left"
            newchatline.TextYAlignment = "Top"
            newchatline.ClipsDescendants = true
            newchatline.Name = "line1"
        end
        UpdateOldLabels(game:GetService("StarterGui").ScreenGui.Frame)
        newchatline:Clone().Parent = game:GetService("StarterGui").ScreenGui.Frame
    end)
end)