diff --git a/solutions/object_oriented_design/call_center/call_center.ipynb b/solutions/object_oriented_design/call_center/call_center.ipynb
index c540c6a6..33272905 100644
--- a/solutions/object_oriented_design/call_center/call_center.ipynb
+++ b/solutions/object_oriented_design/call_center/call_center.ipynb
@@ -110,7 +110,7 @@
     "        super(Operator, self).__init__(employee_id, name, Rank.OPERATOR)\n",
     "\n",
     "    def escalate_call(self):\n",
-    "        self.call.level = Rank.SUPERVISOR\n",
+    "        self.call.rank = Rank.SUPERVISOR\n",
     "        self._escalate_call()\n",
     "\n",
     "\n",
@@ -120,7 +120,7 @@
     "        super(Operator, self).__init__(employee_id, name, Rank.SUPERVISOR)\n",
     "\n",
     "    def escalate_call(self):\n",
-    "        self.call.level = Rank.DIRECTOR\n",
+    "        self.call.rank = Rank.DIRECTOR\n",
     "        self._escalate_call()\n",
     "\n",
     "\n",