As already advised, this is best answered in the legal forum. However, from a dental perspective, all treatment and associated fees should have been explained before treatment begins.
From time to time, changes in the treatment are necessary due to unforeseen circumstances. Those changes and the change in fee should also be discussed and agreed to (barring an emergency procedure).
In new york, we are required to give the patient 30 days to find a new dentist if they are being dismissed from the practice. During that 30 day period we are required to keep the patient comfortable. Failure to do so can result in a charge of abandonment. Your state dental society should be able to advise you what that time frame is in texas.