Unclear communication or misunderstandings can cost you tons of time. Today I misunderstanding cost me about half a day and quite some nerves.
When you are communicating across languages in a language that you are not a native speaker and your counterpart is not a native speaker as well, it gets even more complicated.
In that case, written communication may be better, as you can re-read it or even adjust it.
The spoken word, especially in live calls can lead to hard times.