Obligated to serve your customers

I went to the fourways shop yesterday to get a glass screen cover for my Samsung s5 mini, to be told that you don't keep stock for old phones, only the latest ones and you are under no obligation to keep stock for old phones. As I only got my phone last year and still have another year of my contract before I can upgrade I asked them if they can order me one as I cannot upgrade to the latest and find it annoying that I cannot get accessories for a phone that is still under contract. The lady there called in the buyer and then ordered me a cover that will be delivered today. When I phoned your branch today, I got the same ******* story about how you are not obligated to keep stock for old phones and you don't have one. Has this been ordered and why can't you do orders for people if their contract is not ready to be upgraded but need the accessories? This is a service that should be offered to your clients considering they are bound by contract until their upgrade date.