Telkom upward migration disaster

I'm on 20GB+20GB smartbroadband wireless contract. As this data has become too little for my needs, I was happy to see to that the email which includes my monthly statement, informed me that I could migrate to a bigger data contract and just pay the extra difference for the remainder of my contract. After numerous phone calls to your call centre, Facebook, Twitter, your websites chat service, visiting 3 different stores, no one has been able to assist me with this. They want me to pay off my device and take a new contract which defeats the purpose. When I speak about the information I received in the email it's like it's news to them. The migration information is clear as day online. Who can actually help me?