First off, I love your avatar :) This basically sounds like something you might say if you failed to do something at work, or for homework, something that your boss or teacher would consider to be implied, but that was never actually specified in instruction. Like, boss tells you to prepare invoices for customers. You generate the invoices and print them, but you fail to put them in envelopes, so they can't be shipped. "I was not told to put them in envelopes" (technically you weren't told) Or, teacher tells you to write about your self in English. You do that, however, for some reason, you write in Cyrillic alphabet. When teacher tells you your writing makes no sense, as English can't be written in Cyrillics, you respond: "I was not told to write in Latin alphabet" (I mean, it could happen) Examples are bit dumb, but nothing else comes to mind at this moment. :P

Yes, it is correct. You use it when you go against a command. Like for example, if I told you: You must not lie====> Non devi dire mentire. Then you respond: (La risposta) I was told not to lie =====> Avrei detto che non devo mentire.