New phone repaired thrice and still not working

I bought a brand new Sony Xperia Aqua M2 from Edgars Menlyn in March and was told that it can be returned within 7 days if it gives any problems. After 7 days, it needs to be repaired at Vodacom's Customer Care Centre. The phone worked for about two weeks then gave problems and went in for repairs. After repairs, it worked for another two and a half weeks before giving the same problem and was sent in again for repairs. After the second repair, the phone worked for only three days before giving the same problem ONCE AGAIN. When taking it back to Edgars to request a new device, I am told that it is out of their hands and we need to take it to Vodacom. When I took it back to Vodacom and requested a new device, they told me they can only give me a new device if and only if the current one is deemed irreparable. But how many times must a brand new phone go back for the same problem before then? How much time and petrol should I waste use before then? I haven't even ever carried and used the phone for even a whole month since it is forever being repaired. I need a solution to this very frustrating cycle, please: a new device or my money back please.