This paper presents a novel open-source implementation of a call center, which is compatible with the IP Multimedia Subsystem (IMS) platform, supporting call forwarding and dispatching services, along with video call and chat with file transfer. The proposed solution is called Call Center for IMS (CC4IMS) and following a requirement analysis, the paper discusses the overall architecture and design of the proposed Call Center, focusing on the IMS compatibility and mobility of the implementation. Then, an open-source prototype implementation is presented, which was designed for mobile devices in order to be suitable for distributed and ad-hoc launch at emergency situations by first responder teams near to the location of the emergency incident. Finally, a protocol and message illustration between the CC4IMS and the IMS modules is presented, based on messages that have been actually captured by the CC4IMS prototype and the Open IMS Core, showing that the proposed Call Center confronts with the IMS signaling.