Midas answer on my review not sufficient

I wrote a review about my experience with Midas Worcester. They add my old battery to the new battery"s price and add vat to that. On the same tax invoice the deducted the old battery. First the add the old battery and then gave me credit afterwards. I still have the tax invoice. Why is it so difficult to understand.. I did not get a credt note I still have my receit to prove it. Pls tell me where I can mail it to.