not delivering what they offer

on the 8.07.2015 I received a call from Vodacom. the agent explained to me that it would be more cost efficient for me if they immigrate me to a bigger package. I agreed to this and looked forward to getting more talk time and more data this month. when checking my balance today, I realised that this was not the case. when phoning them today they say there is no record of this happening. how can they offer service to people and then not keep up to their word. this is pathetic! all they could tel me was 'sorry for the inconvenience'. this is unacceptable