There are currently three 56K modem standards, called K56flex, X2 and V90.
Unfortunately these standards are not interoperable and can't connect to the other at high speeds, although they are certainly capable of connecting to each other at 33.6K or less. This means OnTheNet had to make a decision as to which standard to support.
The K56flex standard was developed by a number of different modem companies acting together. The X2 standard was developed by the US Robotics modem company, who make the Courier and Sportster modems. The US Robotics modems are not as common in Australia, which means that there are a lot more modems here that support the K56flex standard. For this reason OnTheNet has decided to support the K56flex standard to provide for the majority of our customers.
However there is light on the horizon for those of you with US Robotics modems: V90 is replacing both the K56flex and X2 standards. This standard should be available in the next few months from your modem manufacturer and will require you to perform a simple procedure to upgrade your modem. Most modems manufacturers are offering free upgrades that you will be able to download from the internet. After this everyone should be able to connect to OnTheNet at the higher speeds.