Identify the unfair aspect with respect to the sentence extracted from an online Terms of Service:
```
the waiver of any such right or provision will be effective only if in writing and signed by a duly authorized representative of fitbit . 

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