I think this falls under a reasonable interpretation of the unlimited.

a reasonable person would understand that there are bandwidth limits both technological and environmental. A reasonable person would expect that the level of service they signed up for would continue or get better over time.

I see two issues.

One is that after a certain amount of data is used they limit bandwidth. If you limit something it is hard to call it unlimited.

The other issue is that early on throttling was not in place. They specifically added throttling to entice users to switch to more lucrative data plans.