How do I protest a warning letter from Yahoo threatening to cancel my account when I don't understand why?

I received an email from yahoo saying I had violated the TOS, but it provided no other information. I called customer service and the guy said I was reported but he couldn't say by whom and to read section 6. I'm 70 years old, don't do , have only personal correspondents, and have had a yahoo acct for years and years. But I could be cancelled at any time. I'm not happy.