Wrong FBA Fees

Ive recently changed the measurements of one of my top selling ASINs to be able to fit my exact FBA fees bracket. Its a fixed cardbourd box that is a 2cm short on every side and 0.5cm short on the height side of the maximum bracket. I've been banging my head tirelessly with Amazons 'robotic' customer serivive to explain to someone that the measurements are 100% WRONG, but as always, they send a sorry, a thank you and a ridiculously automated message, meaning nothing! After some time, they accepted my request to share measurements from their warehouse so i can see too what is it that their seeing so different. I have been told in the past by a fellow Amazon seller that Amazon measure each and every unit and the biggest one they find they tend to cling on to be it even 1/1000. No idea if thats true but based on the 'biggest' theory look at the images i was shared by them. My size tier should be 33x22x2.5 at max with a cost of £1.87. I dont understand how they can me measuring SO irrespondibly and cutting fees that they have zero rights to, and the best bit, theyre not ready to look at their own stupid image and measurements and see how the box has been lifted. Can anyone explain what i should do, we're being charged £2.40 per month, on an item that well about 400 units/pm. The only wrong dimension is the height. I'm really fed up and would appreciate some things other sellers have done that have worked out.

p.s before someones suggests calling, i tried calling, a really rude, half-asleep man called John said they cant do anything on call i have to wait for Amazon to respond in the chat, i explained the urgency and he said; have a great day and ending the call! I wouldnt doubt there all as careless customer service based on how ive been treated in teh last few weeks. Ridiculous.