Mellins optometrists not coming through with quality work

I have been a customer with Mellins optometrists for close to 30 year and never ever had a problem until now. I had an eye test and needed an upgrade in lense strength. I also left my sunglasses to have new prescription lenses put in. WhenIi went to collect both pares of glasse, the readers were fin, but I couldn't see out of the sunglasses. The vision for distant was blury. They took the glasses back after trying to alter the distance vision in the lab. The vision got worse. I asked for new lenses to be made. After many weeks I was informed that mellins would not make new lenses because their expert said that the measurements were absolutely correct. I was told to put my glasses on the end of my nose to look through the section of distance vision or tilt my head forward. I have never heard anything so ridiculous.. I wear my glasses on the bridge of my nose, where they are made to fit. Asking me to pull them to the end of my nose and tilt my head forward was not conducive to save driving. How can the measurement of a R14000.00 pair of glasses be so accurately measured when I could not see cleary out of them and everything was blurry? I never measured the lenses or cut them to size. A mellins technician did that so who is at fault for an incorrect measurement. I got my sunglasses out of the shop and told the lady that I would never be back. There service is not what it used to be and they fact that they refused to take ownership of incorrectly produced lenses is disappointing. I refused to pay for the new lenses because it was not my fault that the lenses did not have the correct vision areas. They are mulifocal lenses. It seemed that Mellins did not believe me when I stated to them that I could not see properly out of them. I want to know how they justify shoddy work and make out that I dont know what I'm talking about. I am adamant that I will not pay for a product that I do not have. They told me they would make a new pair of lenses at 20% discount. Did they then expect me to pay for the first set and a second set? I better not get a bill. As I said before, after almost 30 years I will never return to them again. Bad, bad service