Casing scratched and bent after repair

Casing scratched and bent after repair
Nexus 6P sent to Mobiletouch via Digitec because of a defective microphone. The device came back after 2 weeks:
- Microphone still defective
- Signs of departure on the device, i.e. Case scratched and bent with metal tools
The device was therefore sent in again.
Mobiletouch now demands that the repair be paid for, as this damage would already have existed.
If I could get my car back from the garage with the bonnet broken and the trunk bent, then that would be a case for the judge.