In the context of Service-Oriented Architectures (SOAs), the integration of services is an important aspect that is usually addressed by using specific tools, such as Enterprise Service Bus (ESB). In this paper we propose a framework to perform service integration building on the extension of service interfaces, capturing a class of service integrators that are decoupled from the services they integrate in an SOA. We show how our service integrators can be used in practice by evaluating our approach with Jolie, a service-oriented programming language. Finally, we present how our methodology differs from the standard practice with ESB.