Sterns - 1 year warranty gone down the drain!

I used my Foschini account to buy a Y3 Huawei cellphone from Sterns at Edendale Mall for my son last year. The phone froze while it was still under warranty and he took it to the store on 30 April 2018. The sales lady Thabile received the phone. When we went to check the status of the phone a week later we were told I had to pay R680. I asked why because it was still under warranty. The matter was escalated to the manager, John. He repeated the same story and gave us an account number to pay so they can release the phone. They even suggested it was my son's fault the phone froze. Why would he inconvenience himself so much??? It's not like we were under impression that we will get a new phone, we knew the very old one had to be fixed, period! We then demanded the phone back so we could take the matter up and we were told they cannot release it, we need to pay an undisclosed amount for the fact that they had started working on the phone. I could not believe this as I had bought two phones from Edgars, and when one froze I did not incur such problems since it was under 1 year warranty as well. We need that phone and Sterns have to allow me to exercise my right under that Warranty. I cannot believe the level of unprofessionalism, or is it because they are serving a certain portion of the population in their store? I need answers, somebody help please!