Optical benefits still not paid, months later

I have been waiting for months now for my optical fees to be paid to Specsavers, benefits were checked before I went for my eye test and the lense and frame that I chose is well within my optical benefits, I am only liable for the glass enhancements as that is an exclusion. Why do you charge such exorbitant fees but drag your feet when it's time to pay up. I need my glasses and you need to pay for my optical fees, not a single thing has been paid for, not even the eye test.. Medshield has turned into a joke, late payments and non-payments has become a norm of yours. Really shameful!