Empty promises on contract upgrade

I called vodacom to cancel my contract and got put through to their retentions department. I was offered an extra 500MB free data per month on a particular contract deal, valid from the beginning of March 2015. After checking my existing data at the beginning of this month, I realised that this promise was not delivered upon so duly spent another 1hr + on the phone trying to rectify the mistake. I was assured someone would get back to me in the next 24 hrs. That was 3 days ago. Tried to call again, but have been listening to \african dream"for the past hour to no avail. Over. It. """