Kaff Appliances India — Damaged the hob base while servicing

My Kaff hob igniter has been govong me problems from thw day i ourchased it and recently when i called Kaff service to repair it and set the flame right they came and were not able to remove the screw and so we permitted them to cut the screw head.
But the service person damaged the base and left the cut screw as it os and left.
We noticed it a few days later and when we called to complaon he said me may need to replace it .
Whose responsibility is it to replace it if the service person damages it
The service person says i need to pay and replace it but why should i pay for it when the damage was done by them?