Special Offer was not Delivered

Hi I received a call from Vodacom in Sep17 with regards to a 30gig day and 30gig night @ R399. I requested 2 devices one for my son and the other for myself. The device was delivered 29th Sep and my son activated his on the 1st Oct. On the 7th he received a notification that data depleted. When I queried with Vodacom on the 7th they informed me that it was a 5gig and not 30gig. Ever since than I have called them with no joy. Today I called again and the easy solution for them is collect the device and charge me for what I used. This is unacceptable as they called me with the 30gig off and they did not deliver what they offered. No one at Vodacom taking responsibility for this.