Effective and affordable business-to-business process integration is a key success factor in the telecommunications industry. A large telecommunication wholesaler, supplying its services to more than 150 different service retailers, enhanced the process integration capabilities of its core order management system through wide-spread use of SOA, business process choreography and Web services concepts. This core order management system processes 120 different complex order types.On this project, challenging requirements such as complexity of business process models and multi-channel accessibility turned out to be true proof points for the applied SOA concepts, tools, and runtime environments. To implement an automated and secured business-to-business Web services channel and to introduce a process choreography layer into a large existing application were two of the key requirements that had to be addressed. The solution complies with the Web Services Interoperability Basic Profile 1.0 and makes use of executable business process models defined in the Business Process Execution Language (BPEL). This paper discusses the rationale behind the decision for SOA, process choreography, and Web services, and gives an overview of the BPEL-centric process choreography architecture. Furthermore, it features lessons learned and best practices identified during design, implementation, and rollout of the solution.