Completely unlimited package. 'Mistake 'on website

Good morning I would like to report what happened with Telkom. I am an existing completely unlimited package user with Telkom mobile. My contract is due for an upgrade. I went onto Telkom mobile website for current specials. They had advertised the iPhone 6 plus for R1399 on completely unlimited. When i went to Telkom musgrave I was told they don't have the special. I sent the screen grab of the advert to Ivan the manager. Telkom then went and corrected the error and are now saying it's no longer an error so they can't honor the deal. That is so unfair. I even contacted Telkom pavilion and spoke to the manager Vernon and emailed him also. He didn't even bother to respond even though his store is listed as one offering the special. Disgusting service store manager Telkom pavilion!