Since you received the subpoena and are aware of it you should not ignore it. No, you have not been served properly, but since you did actually receive the subpoena, no judge is going to let you use that as an excuse to avoid a contempt action if you ignore it. Get a consultation with a local attorney for further advice on how to proceed. It is probably best that you have an attorney present during the questioning.
The information provided herein is general information only and not legal advice. The information provided herein does not create an attorney client relationship and is not a substitute for having a consultation with an attorney. It is important to have a consultation with an attorney as the information provided in this forum is limited and cannot possibly cover all potential issues in a given situation.