A subpoena tells you when and where you must appear in court. You may receive your subpoena by mail or in person. When you receive it, you must call the telephone number on the subpoena to confirm your appearance in court on the date indicated.
If you have a date conflict, discuss it with the Assistant District Attorney handling the case before the appearance date. The name and phone number of the prosecutor handling the case is on your subpoena. If you do not appear, without receiving permission from the Assistant District Attorney, a warrant can be issued for your arrest.