A computer system can implement a network transaction service by receiving, over the one or more wireless networks, request data from mobile computing devices of requesting users of the network transaction service. The request data can identify the requesting user and include a transaction request to utilize the network transaction service at a merchant location of a registered merchant. In response to receiving the request data, the system can determine a merchant account of the registered merchant linked to the network transaction service, and identify a customer account of the requesting user. The computer system may then initiate fund transfers between a shared fund account of the network transaction service, the merchant account, and the customer account to fulfill the transaction request.