Hero Motocorp — crack found at tire

Hellow, i am pavel ghosh. I perchased a hero super splendor byke at rudro automobile, burdwan, west bengal at 29/06/2017. A crack has been found at the back tire since 8 month of purchased. I complen tow times at hero service centre. They told that they will call me soon. But, still now they have not called me. Why i use defective tire? I must be greatful to you, if you resolve my problem. Thank you.