Identify the unfair aspect with respect to the sentence extracted from an online Terms of Service:
```
except as otherwise provided on the airbnb platform , service fees are non-refundable . 

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