What language are most international phone calls made ?

It used to be that the vast majority of international calls were from and to North America, Europe and Japan. A very large proportion of these were either from or to America so I'd guess most of the calls were in English.

To make a call in a language, both the caller and the receiver must speak that language. If one of them is not a native speaker, then which other language is most likely for them to know? I'd argue that English is more widely spread as a second language than Chinese is, and despite the number of Chinese people experiencing economic revolution, it's still unlikely that a large majority of international calls would be in Mandarin or Cantonese.

If there is a threat to English in this stat, it most probably comes from Spanish.