A new gradient isn't being chosen every time I open a gui?

My script is supposed to chose a random gradient from a folder of ones that I made. The first time it choses a gradient but then it sticks with it the after the gui is opened again, why is this?

This choses the gradient:

local gradClone

function chooseGradient(player)

    local gradients = game.ReplicatedStorage.UI.PhoneGradients:GetChildren()

    local randomGradient =  gradients[math.random(1,#gradients)]

    gradClone = randomGradient:Clone()
    gradClone.Parent = player.PlayerGui.PhoneMenuGui.MainFrame.ScreenFrame
end

This destroys it when the gui is closed:

function closePhone(player)

    local playerGui = player:WaitForChild("PlayerGui")

    playerGui.PhoneMenuGui.MainFrame:TweenPosition(
        UDim2.new(-0.189, 0, 0.262, 0), -- End position
        "Out", -- Easing direction
        "Linear", -- Easing style
        0.5, -- Time in seconds
        false, -- Overide other tweens

        print("Phone closed"),
        gradClone:Destroy()
    )
end