Service provisioning models underlying service engagements evolve and change as a result of changes in business imperatives. This paper presents a system oriented simulation based framework to handle service engagement model transformation. This framework generates myriad of strategy levers for portfolio managers to choose from in order to handle model transformations. The simulation model along with other components in the framework offers a basis for designing strategy to enable an engagement model transformation by evaluating the impact of each lever on the overall costs, risks and values. The framework has also been illustrated with the help of a case study on engagement model transformation. We believe this study could be of immense value to managers of IT outsourcing firms who are faced with the challenge of handling long term projects that are prone to undergo transformations.