Extra charges after a claim has been made

I last week I went to specsavers at Rustenburg square for the first time for my annual eye test, I chose a frame that costs R2999 and had R1500 discount as per their current promo. I added a couple of extras and everything summed up to R4799. I agreed to that, they submitted to MedAid and everything was paid for. Yesterday I then get a call from them saying that their lab phoned to say that I they have to put an extra hard layer on my frames because if not the frame might break easily and so I have to pay an extra R329 on top of what they already claimed from my MedAid.

Now my frustration is, why does it have to be after I payed for everything that they call to tell me this? At the lab where they make those frames they don’t know that those frames break easily? How can they put out a frame that breaks easily for R2999? Why don’t they put the whole amount from the first place? Why can’t they say that the frame is R3329 once? This is not the way to provide services, this shows that there is no transparency at specsavers, this is ****************. Am disappointed in them