Thinking of changing contracts. Anyone know the difference or have a link on their page that explains it clearly? From the name, my guess is that the "top up" version requires you to buy airtime once your voice/data/sms bundle is finished otherwise you're cut off for voice/data/sms i.e. like a normal top-up except you start with bundles instead of monetary value. The other one I can only guess is the one where you get a shock bill at the end of the month when you've gone into out-of-bundle rates without realizing. If I'm correct, does the "top up" version allow you to buy ad hoc bundles with your airtime or are you stuck using the associated out-of-bundle rates when spending your purchased airtime?