MTN Selling damaged Goods

I purchased a Samsung core prime at Foschini on the 12/***,I was told that if the phone has any problems to return it within 7 days,because the phone was meant to be a gift I only gave it to my fianc? on the 15th. On the 18th of October, the phone kept switching off,I took it to foschini on the 19th and was told that my 7 day warranty stared on the 12th,I was not aware of this,while foschini was helpful, they failed to understand that I was sold a brand new phone with a manufacturer default, and was told that I could not get another phone,I had to send it in for a repair and was told that I would have to pay a repair price of R330,as a loyal mtn customer who has already purchased 2 mtn network phones, I am very unhappy with Mtn poor quality service, as a customer I don't see why I have to pay repair prices for a brand new phone that hasn't even made a call.