Today's wireless networks are interconnected. A network provider can charge other network providers ``access prices'' for serving communication sessions originated from other networks. Meanwhile, the network provider also charges its users directly for using the network services. This paper looks at the proper choices of user pricing and access pricing from a regulator's point of view. We first derive the social optimal user prices when the regulator can directly control them. We characterize and explain how the social optimal user prices change with network's market shares and bandwidth costs. When such direct control is not possible or desirable, we further derive the regulator's optimal choice of access prices, which align the profit maximizing behaviors of the networks providers with the social optimality objective. We further characterize the relationship between the socially optimal access pricing and the market share as well as the users' utility elasticities.