New phone but it is not working, even after repair

I would like to launch a complaint about you store in Scottsville (pietermaritzburg). I bought 2 phones at the store on the 25th of February and on the 03rd March I returned one of the phones as it was faulty. The lady that i assume is a manager told me that I should have brought it back before 7 days of which I dont know how they count, because when i bought the phone it was on Thursday and I returned the phone on the following Thursday. well it was then sent for repairs and I called on the 22nd of march, and they told me it was still being repaired. What must be understood is that I bought the phones for the purpose of using it, and It stayed that long with the repairs. eventually I recieved my phone yesterday (04/04/16). My phone is still doing the same thing that they said they fixed. it is even worse now because it says no sim card. its a dual sim phone, but one sim is working. So now this thing is irritating me because now I have to drive again with my petrol to return it. of which they will sent it for repairs again, and stay with them for another month again. that means I will have to wait for 2 months to use the phone that I bought in February. This is totally out of ord