Disappearance of data

During the middle of December I migrated to another package. I was informed by Vodacom that it will be effective from 1 January, that was acceptable. The morning of the 31 December I realise that I have no data, sms or minutes although the previous day I had surplus data and messages. I phoned Vodacom and was told that although the new package will be effective from the 1 January the previous one has already been suspended and the balance of data etc has been cancelled. I consider this as breach of contract. Vodacom are *****ing from customers. How can you suspend a package before the new one has been activated. I have paid for the data, sms etc which I lost. This is just another example how Vodacom exploits its customers..