Quote vs. Actual Payment Discrepancies

I requested a quote for glasses, withing 2 days I received the quote on what the medical aid will pay and my outstanding amount. 2 weeks later I paid the full outstanding amount on the day I collected my glasses. <br> <br> Suddenly 2-3 months later I received an email informing me that I have an outstanding amount, on inquiring I was told that the medical aid paid short and although they phoned the medical aid before providing a quote, their quote if not final as it is my medical aid and my responsibility. I was told, that it is how it is ... <br> <br> It is not a big amount and not worth fighting for but it is about the principle of the matter, if they take a small amount from a million customer every year, imagine???? So sad, that customer service is not about helping people anymore but how quick you can brush them off, so sad!!!