The open-endedness of telephony platforms is creating expectations among users, ranging from end-users to administrators, to create services dedicated to their activities. Not only is the population of developers heterogeneous, but the technologies underlying modern telephony range over a variety of areas such as multimedia, databases, web services, and distributed systems. This situation drastically widens the expertise required for service creation. We propose an approach to coping with the heterogeneity of both the service developers and the technologies underlying modern telephony. Our approach is based on programming languages. It consists of providing a language that is specific to each developer community with respect to its expertise (e.g., programming skills) and the target application area (e.g., administration). Such languages, called Domain-Specific Languages (DSLs), are organized in layers, accounting for abstraction levels. Our layered approach to telephony service creation is illustrated by two high-level DSLs for end-user service creation, requiring no programming skills, and an expressive DSL enabling the development of expert-level telephony services. We show that layering DSLs greatly facilitates their implementation and verification of telephony-specific properties by leveraging on high-level tools.