Bad quality of Ray-Ban sunglasses

EEMAY

I bought a pair of Ray-Ban sunglasses from Optical 88 in Taikoo Shing City Plaza in 2008.  Unfortunately I find the sunglasses have got rusted and so I approached Optical 88 requesting them to send my sunglasses to the Hong Kong Dealer for rectification.  However Optical 88 refused my request saying that I could not produce the receipt (so ridiculous and irresponsible of the staff of Optical 88, how come I keep the receipt for 2 years!)  Can anyone advise how to get Ray-Bay Dealer to rectify my sunglasses?