I'm saying that the price changes only apply to those that don't choose one of the other offers, or have I misunderstood?
The exact quote is:-
We’ll be changing our call charges by switching to per minute billing. This means all calls from Nov 28th will be charged rounded up to the nearest whole minute. For example – a call of 2 minutes and 10 seconds will be charged as 3 minutes.
The cost of sending a text to any other network on your price plan will now be increasing by 1p. All texts to T-Mobile customers will stay at 6p.
Maybe there’s a better plan for you? Why not join one of our 3 great new plans that offer you loads of free stuff when you top up just £10 a month?
That suggests to me that the price changes will be across the board. Indeed, they are using the price changes as a carrot to entice people to join one of the new plans giving free UK minutes, free texts, or free International minutes. That's how I read it, anyway.