If this was a trial yes, but probation violations are bound by different rules of evidence and the report typically comes in without the person or persons who wrote it having to testify. You certainly can present evidence that disputes the report. Have you browsed through the information in LawInfo's Free Legal Resource Center to learn more about your issue yet? See:
http://www.lawinfo.com/consumer.html and
http://resources.lawinfo.com/en/index.html. You can certainly try to speak to a lawyer to determine what legal options may be available. In the meantime, you may be able to learn more on your own. Search the "Free Legal Resources" tab, or browse the Consumer Resources. Good luck.