In LBL Oil Company v. International Power Services, 777 S.W.2d 390, 32 Tex. Sup. Ct. J. 619 (Tex. 1989), a Texas plaintiff sued a Texas corporation allegedly doing business as LBL Gas Systems on a sworn account and obtained service on the registered agent. 777 S.W.2d at 390. Although he was never served with citation, R. H. Lindley, a citizen of Oklahoma, filed a pro se motion to dismiss the suit alleging he was the sole owner of the unincorporated business LBL Oil Company, it was an "Oklahoma 'dba,'" and there was no jurisdiction over him because there had been no service. Id. After the trial court overruled Lindley's motion upon notice to him, without any amendment of plaintiff's pleadings or further notice, the trial court rendered a default judgment. Id. Upon consideration of Lindley's writ of error, the Court held that because the record established Lindley had no actual or constructive notice of the default hearing, he had been denied due process of law. Id. at 391. The defendant filed a written motion to dismiss for lack of personal jurisdiction. The motion to dismiss was denied. A written answer was not filed and default judgment was taken without notice to the defendant. The defendant appealed by writ of error. In reversing the default judgment, the Texas Supreme Court said simply that once a defendant has made an appearance in a cause, the defendant is entitled to notice of a trial setting as a matter of due process under the Fourteenth Amendment. Id. at 390-91. The Supreme Court did not consider the defendant's written challenge to the trial court's jurisdiction to be a written answer within the contemplation of the rules of civil procedure, see TRCP 46 (every petition and answer shall be contained in one instrument of writing) and TRCP 85 (original answer may consist of pleas to the jurisdiction or other dilatory pleas), because the Court specifically referred to the appeal as involving "a post-appearance default judgment case," as opposed to a post-answer default judgment case. See LBL Oil Co., 777 S.W.2d at 390.