Complain

I bought a nova 71 at game Cresta on 3rd of December and on the 5th it started giving me problem which is it shows black lines all over the screen and on the 6th I went back to the store to explain to them the management gave me attitude telling me that there is nothing they can do do, which is I used the phone only three days and I bought it cash in their store, then they told me that the repair are closing on the 10th and they will book it for twenty one days on January, I tried to explain that I am desperate for that phone I need it, then the other lady came she is working in the store she told me that they will book it at vodacom Fourways it will be be back within seven days, now they are telling me that they booked it at Huawei, which we didn't agree about I told them that I need new phone or my refund because there is nothing wrong I did about that phone it was just new, and I trusted them with my money, am using my airtime to call them, my own money to go there now and then, I would appreciate your help since game store it's playing with me.