Identify the unfair aspect with respect to the sentence extracted from an online Terms of Service:
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users who purchase monthly subscriptions have five ( 5 ) days after purchase to cancel and receive a full refund . 

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. OPTIONS: ["Contract by using", "Limitation of liability", "Content removal", "Choice of law", "Unilateral change", "Unilateral termination", "None", "Jurisdiction", "Arbitration"].