Cloud computing technology presents new challenges in terms of service provisions and consumptions. One of the key issues in this area is to guarantee an agreed level of cloud services to service users. One way to cope with this challenge is to ensure the commitment of Service Level Agreements (SLAs) in which the level of services is formally defined. Although in the literature a number of studies have been carried out on SLA assurance, the majority of them aims to improve the ability of SLA adherence of service providers and focus on minimizing the losses of both parties in a service transaction. However, having such a service-provider- oriented SLA assurance framework is not effective to service users as it is focused mainly on ensuring the benefits of service providers. In this paper, a comprehensive framework will be developed from the service users viewpoint to analyse the ability of SLA commitments of both service providers and service users and ensure the profits of service users by two key steps: (1) design a methodology of transactional risk assessment to assist in selecting qualified services; and (2) devise a SLA monitoring mechanism to monitor SLA enforcement and predict possible SLA violations over the lifetime of a service instance. In particular, the proposed approach will take into account resource performance and network status in the SLA monitoring mechanism as they both have significant effects on successful delivery of services to service users.