Vision Express — Glass breaks by simply cleaning it with cloth

Address: Sion Mumbai vision express

Bought two specs in buy 1 get 1 and cost me around 9100rs in total, only the glasses were around 5500rs and the first time when I cleaned them using the same cloth that they provide, the glass broke like a biscuit, it is so weak and feable, when complained they say that the 5500 rs glass is weak and it breaks so should have purchased the 8999 rs glass, this was not told to us before purchasing that the glass breaks so easily just by wiping it, this is the worst quality glass that I have ever seen, they lie that they told me that this glass does break easily, if they had told me why would I buy it? I told them to change the glass to the 8999rs one and I told them I will pay the difference but they are not ready to do it, this glass is just like chips or thin biscuit. They took 5500 rs and are saying it is easily breakable after it broke. It is their mistake that they don't give correct information before purchasing, for them 9100 rs might be nothing for me it is a lot. They told me they will speak to their manager and get back to me in one day, but today it is the fourth day there is no response from them. I do not want them to fix the same 5500 glass because it breaks easily I want them to replace it with 8999 rs glass which am ready to pay the difference. They are saying if you want that you have to pay full amount again. Why will I pay the full amount when I was not informed while buying that this is very weak and breaks easily, worst quality glass they provide. I want this resolved as soon as possible. Please help.