They are unenforceable for more reasons than that. They also can not prove that you agreed to it, only that someone did.
Also, they can’t change the terms of your previous purchase after the fact. They can make you agree to something new going forward, but if they make your current device a brick because you don’t agree (which they are doing here), then they need to reimburse you for causing the loss of use of your device that you already purchased and was working under the previous terms.