accepted offer, did not deliver, increased price

On28 Jan 2016 my offer to purchase an iphone 6S plus 64k at advertised price of R699 for 24 months accepted by Vodacom Shop in Woodmead, including porting from MTN. They did not deliver on 30 Jan as promised, nor on any day thereafter despite visit and frequent phone calls, including to Manager (Shuan). On 8 Feb prices increased to R749. On 8 Feb Shop phones to say my cell phone is waiting but I must now pay R749 for 24 months. <br> Vodacom Shop claims they did not have stock until day of price increase so I have to pay new price. My submission is shop must honour price as advertised and signed by me 10 days earlier. Their inefficient delivery is not at my cost. Complaint logged at Vodacom customer service but they merely quote that prices were increased.