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

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