fix

main.py

@@ -34,7 +34,7 @@ async def callback(request: Request):
     print("============ callback is being called ============")
     body = await request.body()
     print(body)
-    data = json.loads(data)
+    data = json.loads(body)
     phone_num = data['entry'][0]['changes'][0]['value']['messages'][0]['from']
     mesg_body = data['entry'][0]['changes'][0]['value']['messages'][0]['text']['body']
     phone_number_id = data['entry'][0]['changes'][0]['value']['metadata']['phone_number_id']