I don't think any consumer-protection laws require a company to continue offering a service forever. They could surely stop the ad-free service and start a new

I don't think any consumer-protection laws require a company to continue offering a service forever. They could surely stop the ad-free service and start a new service with ads. But perhaps there are laws requiring companies to get explicit consent and not simply consider it a change in the existing service nor automatically sign people up for the service with the new terms (ads)? I think there should be. I'm not a fan of companies changing their terms at will without clear notification. Clear meaning a plain English description of what's changed, not just "We've changed our ToS, read this long legal document again."