Since the last decade mobile phones have changed people's lives. Mobile phone data can be utilized to derive the spatio-temporal data of subscriptions' whereabouts. It has been possible to study the mobility and traffic estimation with applications ranging from disaster management to disease epidemiology. In this work, we have focused on the use of Call Detail Records (CDRs) to explore and interpret patterns embedded in interaction flows of people through their mobile phone calls. To do so, we consider the geographical context of cell towers to discover structures of spatio-temporal interaction communities in Macau. We have explored the inter and intra-polygon interaction flows. The results suggest that subscriptions tend to communicate within a spatial-proximity community. Understanding such insight is essential for resource optimization in network planning and content distribution.