Harassing to pay money that is already paid

Location/place: Noida

Name of company/service: Tata docomo

I bought a docomo sim post paid connection in august 2012 but didnt paid for the rest of the months so they blocked my sim.but after many calls from them i did paid amount of 3462/- in january 25th 2013 which they asked for and said them to close the account and stop disturbing me later.but these people are again calling me and asking me that connection is still active and i had to pay 890 more.they always give a number to call for cancellation which never works.