Incorrect Pricing

I was due for an upgrade, and went in to MTN Garden Route Mall to look at their promotions. I noticed that they had the Sony Xperia Z3 on MTN My Choice 100 for R369.00 per month. This was not the compact version of the phone but the normal Z3. I took a picture as proof that it was not the compact version of the mobile and showed it to the consultant. His response was that he will discuss the price with the manager and get back to me. Correct me if i'm wrong but if a company promotes a product on their shelves for a certain price they are suppose to give it to me for that price? Today we went in and the consultant said that he has good and bad news. He explained to us that I wont be able to get the contract at the advertised price, but that he has ordered the mobile in case we still want to take the contract. My complaint is that how can MTN promote one thing on the shelve and another in their books. After i told them i want the contract at the advertised price, a week later they changed the marketing material on their shelve.This to me is false advertising and i want to lodge a complaint at ASA (The Advertising Standards Authority of SA) too.