Autofill gui minor bug even after some changes?

I am working on an autofill gui for when you type into a textbox it shows a suggestion. This isnt an error, but everytime I type random upper and lowercase letters, it always sticks to just lowercase instead of how you typed it. My code works perfectly fine, however I'd like to fix this bug.

CLIP: https://medal.tv/clips/56252105/d1337cQiLrCC

TextBox = script.Parent.TextBox
Suggestions = script.Parent.Suggestion
UIS = game:GetService("UserInputService")

function Suggestion(n)
    local names = {}
    for _,plr in pairs(game.Players:GetPlayers()) do
        n = n:lower()
        local tn = (plr.Name):lower():sub(1,#n)
        if(tn == n) then
            table.insert(names,plr.Name)
        end
    end
    if #names == 1 then
        return names[1]
    else
        return nil
    end
end

TextBox:GetPropertyChangedSignal("Text"):Connect(function()
    if string.len(TextBox.Text) >= 1 then
        local plr = Suggestion(TextBox.Text)
        if(plr) then
            if string.upper(TextBox.Text) == TextBox.Text then
                local NameUpper = string.upper(plr)
                Suggestions.Text = NameUpper
            elseif string.lower(TextBox.Text) == TextBox.Text then
                local NameLower = string.lower(plr)
                Suggestions.Text = NameLower
            else
                Suggestions.Text = plr
            end
        elseif plr == nil then
            Suggestions.Text = ("")
        end
    else
        Suggestions.Text = ("")
    end
end)

UIS.InputBegan:connect(function(i,gps)
    if not gps then return end
    if i.KeyCode == Enum.KeyCode.Return then
        local plr = Suggestion(TextBox.Text)
        if (plr) then
            TextBox.Text = plr
            print("Successfully autofilled.")
        end
    end
end)