Under the new plans, if you exceed your data or call inclusions in your plan, you will be automatically charged at the next plan up from your current plan rather than an "excess charge" which could be up to the hundreds or even thousands of dollars. They will also allow existing customers to change over to these new plans as soon as they are released on 1 July 2013.
Another change is that SMS and MMS will now be free. Plans will be specified in terms of included call minutes and megabytes of download as opposed to an obscure dollar cap amount.