I get emails from time to time that "Policy X has changed and will take a effect in X weeks" so at least I'm given advance notice, and am basically OK with that approach as long as the changes are spelled out clearly and not hidden in hundreds of pages of legalese. Maybe an LLM would help here, and translate what the new changes in terms really means so I can decide whether to continue with the service or not. In general I'm OK as long as I'm given enough notice and it's clear what is happening.
The same thing happens with pricing. What does a company do when they want to increase rates, or change their products? They send out a notification that starting on a certain date, the prices will go up. I don't think anyone objects to that. How is a T&C change different?