Identify the unfair aspect with respect to the sentence extracted from an online Terms of Service:
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service contracts : the cancellation right expires earlier if the service has been fully performed by us , the performance of the service began with your prior express consent , and you acknowledged that you lose your right of cancellation once the contract has been fully performed . 

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