Shalu Music — pianos adapters is not working and the shop is telling us we are not responsible for this

Address:

Chatrapati Shivaji Maharaj terminus Mumbai shop no 16 building no 138,Mahendra chambers ,near McDonald's, D,N road,opp CST Mumbai -400001, Mumbai City, Maharashtra

Sir, we bought a casio ctk 2550 piano on monday 28/10/2019, and it was working very well in starting days but yesterday when i plugged the adaptor to the switch board and started playing piano it was not working so i thought the piano is damaged but when i put the batteries in the piano it was working properly so i understood that the piano was perfect and only the adaptor was not working
Today when i called you sir and complained you about this you just said that we are not responsible for the adaptor that adaptor has no guarantee and only the piano has. It has also not been a week also and you are saying we are not responsible and when we came there you were telling again and again it has 3 years warranty.
Sir this is not fair take action for this things also customer are expecting from you and you guys are just hopeless.
We are not satisfied with this.