We consider in this paper a dynamic resource allocation scheme between several Mobile Virtual Network Operators (MVNOs), sharing common radio resources at a Cloud-based Radio Access Network (C-RAN) run by a central operator. We specifically propose a two-level coupled auction so as to enhance resource utilization and maximize the revenues both for the central operator and the MVNOs: at the lower level, end users belonging to a given MVNO bid for resources and, at the higher-level, MVNOs compete for resources at the central operator based on the output of the lower-level auction. We show fundamental economic properties of our proposal: truthfulness and individual rationality, and propose a greedy algorithm to enhance its computational effici...