How do I get my leveling script to legitimately update leaderstat values?

I'm creating a part that gives you exp when stepped on. All of this is running in a server script within the part. The 'expVal' and 'levVal' are IntValues created by another script, stored in a folder found in Players.

part = script.Parent
debounce = true

part.Touched:Connect(function(active)
    local humanoid = active.Parent:FindFirstChild("Humanoid")
    local player = game.Players:GetPlayerFromCharacter(humanoid.Parent)

    local function grantExp(amount)
        local stat = player:FindFirstChild('stats')
        if not stat then return end
        local exp = stat:FindFirstChild('exp')
        if not exp then return end
        local level= stat:FindFirstChild('level')
        if not levelthen return end
        local expVal = exp.Value
        local levVal = level.Value


        expVal = expVal + amount
        print(player.Name..', has been given '..amount..' experience!')
        local expNeeded = math.floor(((levVal+1)*100)^(9/10))
        while expVal >= expNeeded do 
            expVal = expVal - expNeeded
            levVal += 1
            print(player.Name..', is now level '..levVal..'!')
            expNeeded = math.floor(((levVal+1)*100)^(9/10))
        end

    end

    if (humanoid ~= nil) and (debounce == true) then
        debounce = false
        grantExp(1000)
        wait(1) --debounce timer
        debounce = true
    end
end)

When the part is stepped on the code runs (with both values starting at 0) and outputs:

Player has been given 1000 experience!

Player is now level 1!

Player is now level 2!

Player is now level 3!

Player is now level 4!

Player is now level 5!

When the part is stepped on again it outputs the exact same thing. How do I get the script to actually update the values of the two variables, rather than just pretending to and repeating the process from 0 every time?