Don't buy cellphones from Mr. Price bad service

I bought a phone from Mr. price in October the phone started giving problems but I could not take it in as I used the phone for business everyday. I finally handed the phone in on 12 January for a software update..the staff member that helped me said if they can't fix it they will replace the phone it takes 5 to 10 working days to return. I went to the store 4 times and only found out in the 4 th visit that they don't know where my phone is and that it's never been send away for repairs that was 15 days later. I asked for the manager email to lay a complain the manager sent a message with the assistant I must lay an online complain. Today it's 2 weeks after I went there again and still no phone or contact was made. This is Atlantis Branch and people all the phones I bought there is giving problems. How do I go about getting my phone back the cellphone people are never there and they refuse to give me the repair centers number to enquire about my phone.