You have to ask the court for permission to change the date. It is likely the court will want a written motion.
In no way am I offering you legal advice, and in no way has my comment created an attorney-client relationship. You are not to rely upon my note above in any way, but insted need to sit down with counsel and share all relevant facts before receiving fully-informed legal advice. If you want to be completely sure of your rights, you must sit down with an experienced criminal defense attorney to be fully aware of your rights.
I agree with Mr. Deasey, however, you can probably just draft a letter and let the judge know what is going on. You will want to make sure to fax or deliver it to both the clerk and the judge and to call the judge ahead of time to make sure he granted permission. The charge sounds ridiculous. Get an attorney appointed to you (if you qualify) and see if this can be disposed of.
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Keep in mind that you won't be able to talk with the Judge directly (in most jurisdictions), but rather the Judge's assistant or case manager. Call the Judge's chambers (the number should be listed online), and ask for the proper procedures. Do not get into the details of the case at that time because it isn't the proper avenue. You may need an attorney to properly present your defenses and evidence.
No good deed goes unpunished. I am so sorry to hear about this situation. You may want to hire an attorney to help you with the conflict and with the charge. I would think many of us would be very sympathetic and would charge you a reasonable fee.
Best of luck to you,