That seems problematic as all they have really done is announce the closure and disallow new subscriptions. If you prepaid, you still have access. So I don't think you can claim that they're not delivering the service that was paid for. The future is still uncertain.
On Nov 30, however, if the servers shut down and they haven't refunded the unused portion of my prepaid sub, you can be I'll be demanding a prorated refund, and disputing the original charge with my bank if they refuse.
There's probably some wording in the ToS that they think gives them the right to offer time on another game instead, however once they are no longer offering the service then that agreement becomes null and void.