Index: chan_mobile.c
===================================================================
--- chan_mobile.c	(revision 424)
+++ chan_mobile.c	(working copy)
@@ -313,6 +313,12 @@
 	struct mbl_pvt *pvt;
 	char buf[128];
 
+	if (argc < 4) {
+		sprintf(buf, "You must specify name of device and command, e.g. mobile rfcomm nokia ATD123456.\n");
+		ast_cli(fd, buf);
+		return RESULT_SUCCESS;
+        }
+
 	AST_LIST_TRAVERSE(&devices, pvt, entry) {
 		if (!strcmp(pvt->id, argv[2]))
 			break;