Shocking incompetence!

Our 10Gb Smartdata Cotract was set to expire on 17 April 2016, so I made my way to the Cell C store at Nonesi Mall in Queenstown on 29 March 2016 to request an upgrade to the 20Gb Smartdata contract (which was a 24 Month contract on special for R399 a month). I was handed the user agreement which clearly states the 20Gb package I requested which I signed and was given a new router. So fast forward to 1 May 2016, and we receive an sms saying: "10.00 GB of data has been loaded on to your account.Valid until the end of the month.Cell C." Hold on!... 10GB?... it must be a mistake? A quick balance check confirms it... Only 10Gb loaded to our account. After several calls to Cell C cutomer service and the Queenstown store we have established that no one is able & willing to correct this obvious mistake. Customer care tells us to contact the store.. and the store is not receiving any feedback from Cell C... After a string of phone calls I am at my wits end! My fear is that should this complete mess not be resolved... I will have no choice to but to take this matter to the consumer protection agency... as I am starting to suspect false advertising.