Short Paid my claim

I have been short changed in terms of my pay-out. Due to an incorrect description on an invoice. I replaced damaged rims onto my Range Rover through a private purchase after obtaining mandate from Innovation Group. I provided the proof of payment as well as the invoice was provided by the Supplier. The amount was R12 000, for a quantity of two(2) with that said the invoice which was sent by Supplier was incorrect as it indicated four (4) rims. This was an obvious mistake and I asked him to send the correct one which was done. I sent Innovation Group the corrected documents however they failed and refused to amend the claim. This has been done after I have provided all information they needed. Logic would inform any reasonable minded person that you can never find a 4 rims for a Range Rover at R3000 each. This is unreasonable and opportunistic to capitalise on your customers in such manners whereby relevant information and proof is provided. I am not happy at all. I need feedback and someone senior to intervene, because the lady I have been dealing with she doesn't reply to my email anymore.