Is it possible to quip "My package went to Nanjing, but I'm in Beijing; that's the complete opposite Jing"?
In speech, you can say: 我人在'北'京，快递却发到了'南'京. 

It would add some joking effect when you put a bit emphasis on 北 and 南. 

You don't have to say they are opposite literally. Your audience would seize that from your tone, which is the whole point of the joke.