Abstract: A method of processing a transaction between a first user in a first telecommunications network and a second user in a second telecommunications network is disclosed. The first and second telecommunications networks comprise respective first and second transaction processing systems which are not required to have a direct interface between them. A transaction request is received from a first user in the first telecommunications network to effect a transfer of credit to a second user in the second telecommunications network. The transaction request includes an identifier of the second user. A credit value for the transaction is determined. The system verifies that the first user has access to credit sufficient to effect the transfer, and credit associated with the first user is reserved in the first network for the transaction.