Unreasonable notice period after selling the car

I sold my car last week and cartrack is telling me I need to serve a notice period and pay another month. I asked why and they can't even explain besides that it is terms and conditions. This notice period does not make sense. This is like insurance, I don't have the car anymore so I should not pay.

I can't notify cartrack a month before selling wethout knowing that I will find a buyer. The minute I find a buyer I need to sell the car immediately.