Nokia lumia 630 faulty

I purchased my Nokia Lumia 630 on 16th of November 2014, obviously thinking that the phone will be working I chucked the box away.The same month I encountered problems with my phone, when i explained to the lady at MTN (CNA) what problems i have encountered with my phone i was told that they need the box of the cellphone enable for me to receive a new phone or to send for warranty assessment. I had proof of purchase so i see no reason why they need a MTN Lumia box to send my phone away. I paid for the phone not a box....I took another MTN box i had at home and the lady send my phone to MTN warranty division who send the phone back without even looking at it, saying that they will not work on the phone because it is not a nokia lumia box. Thembi at CNA said that even if i get a lumia box the warranty will not accept it a second time. I paid R1999.99 for a phone that keeps rebooting it self, freezing no received calls or make calls. when charging the whole phone heats up. I think that this is totally unacceptable behaviour - response from a company that states that there service and products are of great quality. Confirmastion ( MTN) that the Lumia 630 have soft ware problems???