Mat & May - lost insurance forms for Ray Ban glasses purchase and very poor service

I bought expensive Ray-Ban sunglasses on account and requested insurance. The glasses broke in Feb/Mar at which point I returned it to Mat & May Canal Walk store where it was bought. They then told me that there will be no additional costs due to the fact that I have insurance as requested upon purchase.

Fast forward 6 months, 4 phone calls to ask about the progress and one complaint to customer care, I now received a call from the manager ( who has not been in store once on my 2 visits and 4 phone calls and was supposed to call me back every time ) to say that I never had insurance and there is nothing they can do. They papers must have not been submitted, although I signed the forms in store.

I fail to see how it is my problem that the forms got lost? Surely it is not expected of me to check that a employee does his work? Especially with no manager present and the manager informing me the employee in question is not at the store anymore.

I want a solution, replacement or money back otherwise I am just going to blast it on social media till I get a response