Poor Customer Care ZARA

Bought a shirt from ZARA Mall of Afrika, had a problem with the buttons whereby it unbuttons itself when wearing it. i wore it a few times hoping this problem will eventually disappear somehow but it didnt, I tried to return it to the store recently because it was obviously defective but i was told they cannot scan it back into the system for an exchange as it is last season stock, i found this very poor and bad faith from the store that i so much support, and the company as a whole. I mean the shirt was only R459, surely a manual exchange could somehow be arranged, was then reffered to customercare , i filled in a form in the store and was given an email address to also send a query which i did 3days ago but no one has come back to me and i've made a few follow up emails but still no response, even went to the chat platform on the website but they told me they only handle online purchases. is there a better customer interaction and more effecient way of addressing this? this is very poor and disappointing from such a big brand and damaging my relationship i've built with them over the years. my number is *** should anyone be able to help.