Bonus challenge: Neither of the characters speaks English, so there's a communications barrier not only between the characters, but between the characters and the reader, too.
Feel free to make up your own language(s) for this. You can even have one of them speak
Logophilian if you want.
Ulterior motiveThe purpose of this prompt is to get you to think about the ways people communicate besides speaking. Many of the nonverbal communications techniques and cues you come up with for this prompt can easily find their place in stories where everyone understands one another.
Remember: Characters can transmit a lot more information than just what's in their dialogue.