Comment by lukeschlather

There's obviously a limit to what you can change via ToS. Yes, their ToS says they can alter the deal at their discretion. Adding ads to a premium ad-free tier seems like fundamentally a violation of the presumed contract. (Specifically talking about one-year plans, saying that they can make these kinds of fundamental alterations to the deal mid-year sounds like it ought to be illegal if they're selling one-year plans.)