Consumer Redressal

I used one airtel postpaid modem with special offer and i used for one month than the number is deactivated by the customercare.i paid the bill and i never used that number.but regularly am getting calls from customer care and they are herasing me alot. with out using that airtel number and with out generating bills they forced me to pay the bill every month. I told them entire story everytime but they are not considering my request. please do the need full as early as possible. otheriwise I will file a case in consumer court against airtel.