Child support legal

I have a question about child support I am hoping someone can answer. Its a little long winded but, I had custody of my nearly 18 year old son up until this past Aug. when he decided he wanted to live with his father in another state. I had always received child support up until then and now he is trying to get child support from me. Completely unethical.. lots of details to cover there. Mean while, I had a court date 2 weeks ago and sent a letter and a copy of the current temporary order and attempted top contest jurisdiction. They sent a letter back with a new court date and said I can choose to attend and they will hear the facts that he presents. My question is can I send another letter with financial info and pertinent information or do I have to go to court? I can not afford to travel. I requested a telephonic hearing and was told they do not do that!?