Reliance Mart — Washing machine tub color change

We bought LG front load washing machine in Reliance mart Tirupati. They've sent technician for demo. Technician came with some lg descale packets and he said that for better performance we need to do tub wash for 30 washing cycles.
He said we need to use those packets for better results. So as per instructions given by technician after 2 months we did tubwash. Then drum color got changed. Now Reliance is saying we are responsible for that it won't come under warrenty but it's sold by demo person by Reliance (Lg)
Worst service by reliance