Slightly off topic, but I also got a letter from Telstra saying that from November 22, my $20 plan becomes a $30, regardless that I am 10 months into a 2 year contract period.
I have rung telstra, and the TIO, and been told tough bickies. Telstra can terminate any contract they like without recourse. If you or I did that, it would be breach of contract.
Dont hold your breath on getting an answer other than it costing you more $.
I have just set up an account with another carrier.