You need to contact the Court where your case is filed. See response to FAQ, "Am I in the right Court? If you are unsure of which court to contact.
You should also read any paperwork you have been given from prior appearances in the court for contact information.
In the Common Pleas Court, only the Judge can approve a change in your court date. You will need to call the Judges' courtroom and explain your situation and request the change in your court date. The telephone number for each Judge is listed in the Common Pleas Judges