cross purposes
adverb uk/ˌkrɒs ˈpɜː.pə.sɪz/ us/ˌkrɑːs ˈpɝː.pə.sɪz/
at cross purposes （两人因未意识到彼此谈论的事物不同而）相互误解，相互矛盾，各说各的
If two or more people are at cross purposes, they do not understand each other because they are talking about different subjects without realizing this.
I think we've been talking at cross purposes - I meant next year, not this year. 我想我们谈论的是两码事——我指的是明年，不是今年。