Indeed, and it's in their right to stop offering that when the period you payed for ends.
Its understandable from their point of view to offer unlimited and be awesome but not expect this kind of usage that is not sustainable. So they made a mistake and are correcting it.
It's hard to see it as a deliberate strategy to pull in users and then charge them more when they are "locked in"
Customers are customers, not product managers. It is only natural to make use of a service you pay for.