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