Pathetic and Poor Service Experience

I recently purchased a pair of spectacles from Spec Savers Canal Walk in Cape Town. My medical aid payment went through immediately on the day of order. I was told my spectacles will arrive on the Monday, they didn't call me to give me any update, so I gave them enough time till the Friday and went to collect it. I was then told that my spectacles order got "lost in the post" from the courier to the branch. I was told that on their system it arrived, but they could not trace it. They went searching in other people's orders and still could not find it. They commited to redo my order. My order was then delivered at my house. However, the prescription was obviously wrong as I had blurred vision. I went back to the optometrist for a recheck and they then realized they made a mistake and made the spectacles on the same specifications as my contact lenses (which is incorrect). Now however, they insist on a monetary contribution towards the rectified lenses. I believe I have done everything they asked me to do and thus feel aggrieved by this demand. I should not be paying anything more for what they did wrong. Thank you for your terrible service Spec Savers Canal Walk, you will never see me again!