BEIJING — If you've ever had trouble ordering at Starbucks, just know you probably have plenty of company: millions of Chinese coffee lovers.

When one customer recently posted an open letter online to the chief executive of Starbucks in China to complain about the way the American coffee chain calls its different size cups, the commiseration started to pour in. The original post was entitled: "When will you stop thinking that your customers who order a medium cup of coffee are ignorant or stupid?" Despite it's extra large title, the letter quickly fired up some like-minded clients of the Seattle-based chain.

Lin Guotong, the online letter writer and a loyal Starbucks customer since 2010, says he's irritated by the barista's same-old questions: "Are you sure the medium cup is what you want? In our store, the medium cup is the smallest cup." Starbucks in China offers the zhong(中-medium), da(大-big), and chao-da (超大，super-big). Lin, proud holder of a Starbucks Gold card, says the staff at the popular coffee chain should know that he's a loyal customer and not ask him about his choice of cup size each time he visits. He says he's used to Starbucks branding its cup sizes with "low-class promotion methods."

Chinese customers have long expressed annoyance with names given to cup sizes at Starbucks. "Why on Earth do you want to call the smallest cup the medium cup if you have only three sizes on offer? This obviously runs against common sense," one customer said.

Luo Yonghao, a Chinese internet celebrity, recently posted a video on his blog criticizing the American giant, which has more than 2,200 stores across China. In the video, Luo is corrected over and over again by a female barista who insists on him calling a medium cup, large. In despair, Luo smacks his own face in frustration.

In the US, Starbucks has four cup sizes, and none are called "small." There's "short," and then medium is a "tall." Any bigger than that, and you are required to speak Italian, which at least is a bit easier than Chinese.