Poor service rendered

I bought a phone at Sportscene Greenacres Port Elizabeth on the 29th of October 2017 within a month since i bought it it got faulty on the 25 of November 2017. I returned the phone on the 27th of November 2017, they booked the phone and promised to me after 14 days. I called them myself on the 16th of December 2017 and they promised to call me back again and no one called me.

I've called again on the 20th of December and requested to speak to a manager, they then called a lady which claimed to be a manager and she took my details down promising that she will ask the cellphone lady to call me back...STILL NO ONE CALLED

I then visited the store on the 23rd of December, i requested to speak to a manager. They called a lady which told me she never spoke to me on the 20th...I then asked her where is my phone, she told me to wait for cellphone lady. The cellphone came back and it was the same girl who sold me the phone, i asked her where is my phone.....she told me about repaires office and she promised to call me on the following week which starts on the 25th but up until today they never respond to me.....i dont know why they cant give me my money back