There are over 7 billion global mobile service subscribers generating trillions of calls, messages, and data sessions annually. Servicing this demand whilst attempting to offer compelling propositions in a highly competitive market environment, is an on-going challenge for all Mobile Network Operators (MNO). In many cases, MNOs are constrained by traditional billing systems or traditional ways of forming a contract with the subscriber. Diadem will lever the innate ability of blockchain technology to provide a secure and de-centralised environment, and the power of electronic smart contracts, to provide an alternative billing, payment, and subscriber contracting architecture for MNOs. Diadem provides a billing, payment, and subscriber contracting system for Mobile Network Operators (MNO) using de-centralised smart contracts on a blockchain platform. Abstracting the contract and billing mechanism from the operator’s traditional business support systems and moving it to a blockchain platform provides huge benefits for MNOs such as contract flexibility and transparency, additional security, cost reduction, and scalability.