Brand new phone sent in twice - Still not repaired

I renewed my contract with Vodacom in Nov / Dec 15. I received a new Handset Samsung J1. I started having problems but could only get to the shop in January to take the phone in. They did a software upgrade and sent my phone home. (This took them a week) I then had to take off and collect my phone. My phone started again with the same issues so I had to return again. They took the phone in and kept it for another week whilst doing a software upgrade...again. I am now going to send the phone to them for the 3rd time. I have spent hundreds of rands on taking time off, petrol and parking just to get the phone back woth all the same problems twice. I am beyond the point of tired of begging Vodacom for sevice. This is a handset and should have a 2 year guarantee. It should not be this impossible for the clients to use the handset which we get billed for on a monthly base.