Unprecedented advances have been seen in E-commerce with the spread of digital commerce and customer relations on commercial websites, such as Amazon. As a result, investigation of this type of communication has opened up new horizons for discourse analysts. This study aims to identify the complaint strategies used by customers and the reasons behind them. With this in mind, the researchers formed a corpus of the most helpful negative reviews posted on Amazon. Similar to previous studies on complaints in spoken communication, the present analysis investigated the different complaint strategies speakers used to formulate their complaints. Additionally, politeness strategies and face concerns were examined in these complaints. The results indicated that customers used eight different complaint strategies, the most frequent being showing their disappointment, anger and annoyance while making their complaints. The reasons for their complaints were delivery problems and unhelpful customer services behaviours.