Cellular phone networks are often paralyzed after a disaster. However, the infrastructure damage is difficult to be fixed within a day in the case of the disruptions caused by disasters. This paper addresses the challenges of proximity call communication in emergency and disaster areas. 3GPP Release 12 defines proximity service (ProSe) for public safety. When two users are making proximity call without infrastructure in a diaster, the on-going call is force-terminated as the users move out of the proximity range. In this paper, we propose a method to provide transparent service continuity via extending the ProSe call through a common ProSe neighbor without the need of interacting with the radio access network. Then we propose an analytical model to compute the call completion probability with the assist of common neighbor tunneling.