Service supply chains have changed over the last decade from internal and integrated operations to interorganizational supply networks where many interdependent organizational units provide fast and high-quality services to demanding customers. All these units have their own strategic interests and unaligned operations. The issue of how to coordinate strategy and operations in these decentralized supply networks is of paramount business relevance, especially in innovation-driven industries such as telecom. In this presentation, an approach is presented to overcome this issue. Suppliers that normally are rated on aspects that are under their direct control, so-called "defensive KPI's", can instead be rewarded for their contribution to end-customer related performance items, such as the percentage of error-free orders. These so-called "offensive KPI's" arise only from a thorough and shared understanding of the root causes of operational performance across organizational boundaries. Such understanding is created through group-model building meetings with staff involved , using system dynamics methodology. In doing so, both the "soft" and the "hard" aspects are confronted. This approach is described in a case involving the turnaround of the buyer-supplier relation between KPN Telecom, a medium-size European Telco, and Atos Origin, a leading ICT services provider in Europe, that the author supervised directly.