Legal Question in Consumer Law in California

They are wrong. Unless the clause specifically says not more, no court is going to accept their claim that you have to give notice only on the 30th day before the contract expires. Even if it DOES say that, most courts will find a way to refuse to enforce it, including principals of adhesion contracts and reasonable interpretation. Unless the contract is crystal clear that only notice on the 30th day counts AND there is no question but you knew that was what it said, what it meant, and were in agreement with it, I can't see them winning that issue.