Despite increase in deployment of BS, MNOs are still faced with the daunting challenge of providing adequate coverage and capacity in indoor environments. Furthermore, the trust-less environment in which MNOs operate makes it further challenging to achieve interoperability across carriers. Recently the concept of mOs has emerged as a promising solution through deployment of small cells. However, their success has been severely hampered by the absence of a framework for creating and managing business agreements between key stakeholders, i.e., MNOs and mOs. This article proposes a blockchain-enabled SDN approach for managing radio spectrum access between MNOs using smart contracts over small cell networks. Specifically, our solution uses a smart contract to validate transactions between MNOs. Simulation results show that our solution guarantees seamless handoff and high availability between different operators in contrast to a break in connectivity in the absence of an agreement.