Not disconnecting my connection which i don’t need

Location/place: pune

Name of company/service: Reliance communication

Sir,
i was using Reliance netconnect+ plan for internet usage.My number was 9372388072.
But after working for few months,the device stopped working.I went to the service center,but they said nothing can be done,its dead.Though it was still in the warranty period.But the catch was.The salesman,who sold me the connection,told me there is no separate bill for the device,and it was not given to me.I somehow got the device repaired from market,and paid my outstanding bills. But after working for 2-3days,the device again broke. I was so much faded,i went to the reliance store at vishrantwadi,pune, and told to discontinue my service.My outstanding bill at that time showing in there system was Rs.381. I offered them,that ill pay the bill,and you discontinue the service.But they said to me,to discontinue you’ll have to pay Rs.700.I asked them but your system is showing 381,they said no but you’ll have to pay for next month rental too.I left the shop without paying.After that i called the customer care and told them to disconnect my service. But again started the same cry,that “you are our premier customer,we don’t want to loose you.U just visit the reliance store once”.
But at the end,they didn’t disconnected my service.

Now my concern is,may be after 3-4 months,they will wake up and will ask me the pay the bill for all these duration,in which i havn’t used the service.I have also taken the effort from my side to discontinue,but they didn’t.
I need the forum,to help me in this situation and act accordingly.