Identify the unfair aspect with respect to the sentence extracted from an online Terms of Service:
```
if you requested to begin the performance of services during the cancellation period , you shall pay us an amount which is in proportion to what has been performed until you have communicated us your cancellation from this contract , in comparison with the full coverage of the contract . 

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