An exemplary multi-line communication system presents a single on-screen user interface on a communication device. The communication device is configured to conduct communication sessions over both a first communication line associated with a first mobile directory number (“MDN”) and a second communication line associated with a second MDN. Within the user interface, the multi-line communication system presents an aggregated communication history including communication records representative of communication sessions associated with both the first and the second communication lines. The multi-line communication system detects a user action with respect to a communication record within the aggregated communication history, determines that the communication session represented by the communication record is associated with the first communication line, and initiates an additional communication session over the first communication line based on the determination that the communication session is associated with the first communication line. Corresponding systems and methods are also described.