The 3GPP standards for IMS (IP Multimedia System) provide access to multimedia services with robust procedures for QoS management. However its scope is limited to session initialization only, thus lacking follow-up or monitoring functionality; neither does it tackle SLA (Service Level Agreement) differentiation. A tempting approach would be to leverage the standard architecture by assurance processes based on TMForum's eTOM framework. This scenario would however necessitate a set of general business processes and would require a projection of IMS processes towards the eTOM. The work presented here follows this strategy, providing IMS services monitoring functionality based on eTOM processes able to provide SLA assessment and Service Assurance. It uses the BPEL language for orchestration and SOA elements to implement the distributed architecture.