The attorney should show you the Substitution of Attorney, or you could check the court file to see if it has been filed. If he is not the official attorney, you should continue to deal directly with the other party. However, if that party then tells you he wants you to deal with the attorney on the discovery issue, I would respond to that attorney. In any event, if you did not produce discovery, the fact that the wrong person might be demanding that you produce the discovery does not, at the end of the day, relieve you of your responsibility to respond to discovery. Hope that answers your question.
THIS RESPONSE IS NOT LEGAL ADVICE. IT HAS BEEN PROVIDED FOR EDUCATION AND INFORMATION ONLY. Mr. Mann is licensed to practice in the State of California. There is no implied or actual attorney-client relationship arising from this educational exchange. Moreover, the facts provided by you were not sufficient to allow Mr. Mann to advise you specifically regarding what you should or should not do. You should speak with an attorney licensed in your state, to whom you have provided all the facts before you take steps that may impact your legal rights. Mr. Mann is under no obligation to answer subsequent emails or phone calls related to this matter, or to take any action whatsoever.
Yes, a Substitution of Attorney must be served on all parties. So, if you have received a letter from an individual claiming to be the attorney of the opposing party, but you never received any kind of notice that said party was being represented by counsel now, then you would ask this attorney for a copy of the Substitution of Attorney that was filed with the court (pursuant to CCP Sections 284(1) and 285).
This attorney is licensed to practice law in the State of California. The laws of your jurisdiction may differ and thus this answer is for informational and educational purposes only and is not to be considered as legal advice. Since all facts are not addressed in the question, this answer could change depending on other significant and important facts. This answer in no way constitutes an attorney-client relationship.