Wis. Admin. Code ATCP § ATCP 132.02
No shop may perform any repair that has not been authorized by the customer. Before a shop starts any repairs whose total price may exceed $50, a shop representative shall record the repair authorization on a written repair order under s. ATCP 132.03.
Wis. Admin. Code Department of Agriculture, Trade and Consumer Protection ATCP 132.02
Customer authorization is required for all repairs, including repairs under $50 and repairs on vehicles brought to the shop without face-to-face contact between the customer and a shop representative. Authorization may be given in person or by telephone, or by any other form of communication between the customer and the shop. Authorization to perform a general repair implies authorization to perform the specific repairs that are normally included in that general repair. Merely reporting a problem or malfunction does not, by itself, constitute authorization to repair the problem or malfunction.