Now would be a good time to have a functional FTC commissioner. Doing a bait and switch like on a product that was sold with a set of features should be illegal. If I buy a car and the sales guy stops by my house the next day to take back the wheels, it would rightfully be seen as ridiculous.
Don't these usually come with ToS or something that has you agreeing that they can change the service any time?
Like a car park can say they're not liable for your car's safety, it doesn't mean they can steal your car. A roller coaster can say they're not liable for injuries but if they didn't inform you it's dangerous for pregnant people or if they violate some safety law, they're probably liable.
The bit about changing terms of service probably gives them some leeway to deal with law changes and stuff. If they're purposely being misleading to play bait and switch, that sounds like it's breaking a law somewhere.