Belittling, service and attitude from a self appointed technician.

I am totally disgusted and ashamed of the poor service and belittling I received from the store manager at PEP stores in Melville, Campus square, Johannesburg. On the 20 March 2019 I bought a Stylo Flame handset from the Pep in Melville. On 21 after using the handset for less than 24hours. I then realized that the handset had a speaker problem which persisted on an on and off basis. I then decided to attempt to return the handset for a new one as I needed a handset that was 100% functional. Upon being served I showed a lady who was working there the handset and told her my issue. Mind you I still had the slips original packing, the works. She then told me that I should wait for another lady to help me as she does not deal with customer complaints and exchanges. I then was helped by a different lady who asked to see the device, ( mind you she had no decency to even introduce herself to me). Miss Rosimah, ( I only got her name after telling that I wanted to lay a complain), inspected both the phone and myself then asked one of her colleagues to call my phone so that she could check if I was not lying. After she called my phone using her phone she then told me that the phone was working perfectly and that there was no issue with my phone. In fact she went on to emphasis that her phone , ( which is samsung galaxy from what I could make out) was even performing poorer than my R140-00 handset. A statement I find quite belittling.... She then further stressed that my phone cover had scratches and it looked like it had been through hell. What ticks me off the most was the fact that this handset was not even 24 hours old and I was already experiencing problems only to have this women treat me like *******!! Miss Rosimah then told me that she would not exchange the phone because 1. She found no fault with the device and 2. She claimed the phone had significant damage to its cover. What interests me is to know if she was even qualified to make such a claim ? Because now I am stuck with a faulty device and I do not know what to do. Please help