HTC — Servicing problem

Address:

713201

Mymy handset - htc desire 820 was having a battery issue. I went to the authorized service center - tvs electronics ltd., address- j k pal lane, m.K. Plot, benachity, durgapur- 713213. They have replaced my battery but after that updated the phone's software to a new version which is not supported in the handset, now there is a on screen problem happening imy handset and they are telling to replace the motherboard of the handset which is costing inr 9500/-.
If they are not having the genuine software is it the customer's fault? why should i pay that inr 9500/- without my fault? i request you for an immediate solution of my problem.