What can I do if I was charged with theft for selling a laptop because I wasn't paid for the repair that I have done?

A person gave me a laptop to repair, we agreed on a price and that it would be ready the following day. I repaired it and the following day visited his house and showed him that it was repaired but the costumer never had the $75 for the repairs. He told me to go the following weekend and so I did but he always said that he had no money. This went on for 5 months. After 5 months I sent him a written notice for him to at least pay $20 for the repairs. Within that week or the item would be sold to recover expenses. Another month passed and he failed to come forward with the money (he did not paid anything at all, no deposit etc.) After 6 months, I sold the laptop, when he found out. He gone to make a report that I have sold his computer without his consent and I was ended up been charge for theft. He said the laptop was valued at $800. Now I have been adjourned until December 6. It is to know that the officers are his friends. What can I do? What objections can I use? What can I say to the judge? Can it be dismissed?