Sounds to me like they have oversold their market footprint and can't keep up with demand - 5GB cap? Moving customers to 3MG from 6MG. Oversold, over saturated and trying to devise a way to charge more. Let's play tiers. In the end, they'll get less - customers will move on to another vendor.
It happened in my area. And it only took them 2 years to figure it out....
