Just because a customer doesn't English good doesn't mean they deserve any less service than any other person who English better. 

It's honestly ridiculous that you feel entitled that customers have to put in "effort" for you to assist them. They're trying to get assistance from you but according to the story you cut them off before they even got an attempt to put in whatever necessary "effort" you require from them for you to do your job.

The point of customer service is to assist the customer and help them with whatever it is they need help with. You're just bad at your job, honestly. Treating a customer like that on such a basis is simply inexcusable. 

You live in America, the country literally founded by immigrants. You're going to encounter people who don't speak English very well for a long time. If you can't handle that, then there won't be very many suitable jobs, if any at all, for you.