大量的研究已经表明提供高品质客户服务和有效投诉处理的公司，可以收取额外费用并且能够提高顾客忠诚度。
Multiple studies already show companies with high quality customer service and effective complaint handling processes can charge a premium as well as increase loyalty.
投诉时语气礼貌且态度坚决通常是最有效的，尤其是当消费者能说明这个物品哪里出了问题时，更加如此。
Complaining is usually most effective when it is done politely but firmly, and especially when the consumer can demonstrate what is wrong with the item in question.
当面投诉或写信投诉通常更有效。
Complaining in person or by letter is generally more effective.
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