Idea Cellular — idea cellular is harassing

I was a idea postpaid customer and i have paid the bills till 11 jul 2017 and called customer care to deactivate my sim but no one has forward my call to concern department and i called them twice after that and stopped using sim. Now idea is sending email with legal notice header. As per there customer care if you are a postpaid customer you have to pay the bill even if you not using sim till it get deactivated. Idea intentionally don't forward call to cancellation team so customer cannot go ahead with cancellation and they can get illegal money by harassing them. If they want to go court i will go but not ready to pay amount which i have not used