Vishal Mega Mart — tandem electric iron

I have purchased tandem electric iron from vishal mega mart located in uttarahalli bengaluru on 15/01/2019. After 4 months it stopped working since it was in was in warranty period i took it to vishal for either repair or exchange but they didn't entertain me at all. They told we can't do anything u talk to customer care. While calling to customer care got to know that it's invalid no. It was clearly written on the warranty card that vishal mart is responsible for any fault within warranty period and purchase this product due to vishal name associated with this product but they are denying and no response from customer care. Please help in resolving this issue. It is cheating from vishal mega mart n if this continues to happen nobody will believe in vishal. Moreover they r deteteoriating there brand and mkt value like this by fooling and harassing their customers. Pls resolve asap.