Wis. Stat. § 134.37
Any person connected with a telegraph or messenger company, incorporated or unincorporated, operating a line of telegraph or engaged in the business of receiving and delivering messages in this state, in any capacity, who willfully divulges the contents, or the nature of the contents of a private communication entrusted to the person for transmission or delivery, or who willfully refuses or neglects to transmit or deliver the same, or who willfully forges the name of the intended receiver to a receipt for any such message or communication or article of value entrusted to the person by said company, shall be imprisoned in the county jail, not exceeding one year, or be fined not to exceed $500, in the discretion of the court.
Wis. Stat. § 134.37