> Could anyone win a lawsuit against a serviceprovider for (completely within the terms of the contract) not wanting to provide a service anymore?

The problem is that with a 1B+ people dependent on the product, shutting it off wouldn't just get you lawsuits, but also visits from scary men in suits and extralegal actions.

You may very well be coerced into switching the service back on - at the end of the day, contracts are just pieces of paper.