2 sentences for 认错 (rèn​cuò — mistake someone for)

1. 你们肯定是认错人了。

   nǐ​men kěn​dìng shì rèn​cuò rén le.

   You must have the wrong person.

   Source: OpenSubtitles

2. 你认错人了。

   nǐ rèn​cuò rén le.

   You've got the wrong person.

   Source: OpenSubtitles