In face of pressure from politicians and constituents public agencies have to collaborate with each other to offer a one-stop shop. The emphasis shifts from vertical to horizontal coordination and integration, which requires the making of commitments between public agencies and the fulfillment of these commitments. Consequently accountability shifts from hierarchical to commitment-based accountability. In this paper we propose an agent-based modeling approach aimed at modeling coordination of activities and commitments. Software agents are used to simulate the actors and dynamic behavior of the organization network. Our approach supports decision-makers to improve cross-agency business processes and checks if the commitment loop of request, promises, reports on status of the commitments and justification is completed. We apply the proposed modeling approach in a case study of a virtual business counter and test the approach using a number of interviews.