At any time before the case is called for trial, the defendant may file a written answer to the complaint. The answer need not be in any particular form. The court shall enter a general denial of the complaint on behalf of the defendant if the defendant does not: file a written answer; or admit the material allegations of the complaint in open court. To ensure that the defendant understands the nature and substance of the complaint, the court shall read or explain the complaint to the defendant if the defendant: appears for trial without filing a written answer; or files a written answer admitting the complaint and is not represented by counsel.