SPECSAVERS STANGER

I recently went to the Spec-Savers Stanger KZN branch in the KwaDukuza Mall for my yearly check up. I clearly advised that what ever the charge is, that I dont want any shortfalls, the price they quote me must be covered fully by my medical aid. I was assured it would be. I was then offered the special of getting a pair of sunglasses to the value of R1000 and this would be covered. I chose my pair of sunglasses and the lady put them away for me. When the time came to collect my glasses, I get told there is a R800 shortfall to pay because of the sunglasses. I said I was not told that on the day. I was told that everything was covered. So now I had to give the sunglasses back. How does that work??? then I get my multifocals and I use them for the first time in front of my computer and I cannot see through them, its blurry. I tilted my head forward and backwards and I cannot see clearly. What do I do??? Im so upset, I need to use these glasses for the next 2 years. It cost me over R4,500 for one pair of glasses and im not happy with them. How do I get help with this.