We investigate in this paper the access selection and joint pricing problem in multi-operator wireless networks. The problem is formulated as a Stackelberg game, where cooperating service operators first set the service price to maximize their revenue. Then, the home operator of the mobile user performs the access selection process among the service operators, in order to maximize its own profits and its client satisfaction, in terms of perceived QoS. Competing operators decide the service price following a number of defined pricing schemes, and the home operator uses a hybrid utility function for the selection decision. We consider the Nash equilibrium as a solution of the service price setting game, where the best response is presented in function of the adopted pricing scheme. Simulation results show the efficiency of this multi-leader follower game for the access selection in a multi-operator environment, and illustrate how operators' cooperation enhances network performance and improves operators' revenue.