The adoption of IT-based interfaces to monitor and control telco capabilities is a consolidated approach. In such a scenario the end-users design composite services that orchestrate functions implemented through one or more resources managed by telecom operators. In addition to the issues that have to be faced to support the design of composite services in general, in this case it is also necessary to face issues that are specific to the telco domain. In fact, telco services strongly rely on the processing of asynchronous events generated by resources; moreover, they usually handle large and dynamic sets of concurrent processes that execute long-running transactions each of which includes interactions between the composite service and the telco capabilities. The complexity of the telco domain suggests to define a set of patterns to ease the development of composite services. The goal of this paper is to propose such patterns and to show how they can be implemented both as plain Java objects and as BPEL processes. The pattern based approach is illustrated by means of a service which takes advantage of the combined use of multiple patterns. Moreover, the paper suggests some improvements on the definition of the interfaces and on the reference model for the development of composite services.