老板是外国人.下班时间已经过了.却因没向他们打招呼要走.就被扣了200！我该怎么办

apply for personnel department via email & pls let the department note the reason.
foreigners have theirself weaknesses, e.g. they don't know chinese language, they can't grasp daily traditional issues happened in chinese company, and so forth,so u can tackle things according to this situation depanding on ur need

Tell him the fact, maybe there is misunderstanding.

Otherwise, say bye to him everytime when you leave.

老外很多都很不像话的，不要觉得老外都是很好的。要维护自己的利益。