AT&T Corp has sold the German operations of its AT&T Istel services unit to Rutherford, New Jersey-based Computron Software Inc. The company takes over the operations, customers and products. Computron made a $400,000 down payment and will pay $1.4m in January 1997. It says the acquisition provides it with more than 100 new customers and 43 experienced business software and implementation personnel in Germany.