My guess would be (without knowing how the backend of their system works) is that the initial 12 month agreement needs to be paid, and once you are past that you are considered "month-to-month" by the system, so they have to manually override an 'end date' extension. Rather than go through the system for every member to figure out who they need to do that to, they are relying on the customer to call in to do so.
Give a database developer 20 minutes and I bet they'll have figured out a way to automate this if not actually develop the code. Of course, that's reliant upon the data being readily available in a usable format, which I'm assuming not.