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