I'm unable to upgrade an active LineRate license from one tier to the next

So, another question. How do I actually cancel my subscription and then purchase a new one?

This document about configuring licensing does mention that you must cancel and purchase a new one: If you want to upgrade your license, you need to cancel your existing license on linerate.f5.com/try, then purchase a new one.

I can see on my subscriptions list at https://linerate.f5.com/try, and I see the cancel button here https://dl.dropboxusercontent.com/s/sfz417b0dzcrznp/2015-11-25%20at%209.35%20AM.png, but it's not obvious how I'll be able to repurchase a license for the current system I'm using.

Do I actually have to entirely replace the current system with a new installation? This is a running, production system serving traffic and will be serving traffic over the next few days, which is our biggest time of the year.

I'll be honest. I really, really love the LineRate software and I seriously want this installation to be hugely successful so that we can use it in our other data centers, but I can't risk my job, or many company's well being on a hokey, broken software licensing model that is great for F5, but is constantly screwing over the customer. What is going on?