Solutions to the cellular network bandwidth problem have been presented by the community such as usage of alternative wireless (e.g., 802.11 WiFi) network and peer-to-peer (P2P) file sharing over a group of wireless devices. However, often the theoretical and simulation approaches for file sharing within multi-radio P2P groups hide the complexity of systems and networks in real scenarios such as heterogeneity of phones in a P2P group, issues with scheduling policies within a group of devices, group formation etc. In this paper, we present Sangam, an efficient cellular-WiFi group framework for file sharing where we address extensively system and network challenges in file sharing for real phone group scenarios. The Sangam framework accounts in its protocol, policy and algorithmic designs for (a) heterogeneity of phone group devices in terms of CPU and power levels, (b) different sizes and numbers of chunks in P2P part of the group-based content distribution, (c) hybrid scheduling policies for chunk dissemination within multi-radio wireless group environment, and (d) different group sizes. Sangam validation shows the impact and difference to simulations when considering real implementation of video file sharing within a cellular-WiFi group of Android phones.