False advertising / retracting promotions (Nov)

<p>So I'm due for in upgrade, mtn cellular intelligence sent me a link to their site so I could decide on a phone. On the 1st, 2nd, 3rd nov I check the site (mtndeals.co.za) decided on a iPhone 6s Plus 64gb, that was advertised at R499 a month, I screen dumped the deal, I go on their site again today (4 Nov) and and it has changed to R689 a month! So as per CPA, they will have to give me that deal of R499! Am I in correct in saying!? Then I go to Mtn east rand mall, extreme rude employee telling me it was an fault! And there is nothing they can do! Really!! I would like a response!</p>