Rapid growth of bandwidth demand from smart mobile device usage forced telecom service providers to expand network infrastructure. Increasing investment in bandwidth naturally drives expenses up, but will not drive the revenue up accordingly due to the flat rate policy. Moreover, customer satisfaction declines due to congested networks caused by limited investment on network infrastructure. In this study, we adapted some core functions of NG-SDH (Next Generation-Synchronous Digital Hierarchy) network to develop a dynamic flow-based bandwidth management approach to improve bandwidth utilization. The proposed approach can increase utilization of existing NG-SDH networks effectively and serve more customers without sacrificing quality of service. In our experiment, we observed an increase of bandwidth utilization up to 78.3%. More service policies for customer can also be provided.