Medical Aid Misuse

A month ago I went to the optometrist to get new glasses,then I get first quote which I sign for as that would be what my medical limit be,however just before all is done she suggests that I need to change the frame selected as my script will not hold on that frame.We then discussss that they should not process claim until I have confirmed with my medical aid that the claim will be covered as I was expecting my savings to be up the following month, however their assistant goes ahead and processes the claim when I call them I discover that they have claimed.The assistant is now pleading with me to at least pay half of what was claimed for and I refuse because that was not my instruction and will certainly not have that money. I call to speak to the manager and each time she is not available.Finally when I get hold of the manager and request the quote I discover that they amended the amount by hand and processed claim while I did not sign for the change and they expect me to pay .