In Buxani v. Nussbaum, 940 S.W.2d 350 (Tex. App.-San Antonio 1997, no writ), the owners of a jewelry store had a written agreement with a contractor who was to remodel their store. Id. at 351. The Buxani contract contained a provision that stated: "Any alteration or deviation from above specifications involving extra costs will be executed only upon written orders, and will become an extra charge over and above the estimate." Id. Although the written contract required changes to be in writing, the Buxani Court held the evidence sufficient to show that the owners "assented to the terms of the oral agreement through their conduct; they allowed the items to be installed and the services to be performed without objecting to anything until the time for payment arrived." Id. at 352. The court also observed: "In a contract implied in fact, which is the same as an express contract except for the manner of proof, the element of mutual assent can be inferred from the circumstances of the transaction." Id. The Buxani Court concluded that the evidence supported the existence of an oral contract and affirmed the trial court's judgment because the owners breached the oral contract under which they agreed to pay for the changes they had ordered. Id. at 353. Disregarding a term of a written contract requiring that extra work be authorized in writing may result in a finding of waiver. Id. at 352.