Airtel - Bills to be paid

Hi,

I had taken corporate connection with Airtel. No is 9901912737. I stopped using the service in Sep 2011 and I personally went to Airtel office and asked them to stop the service for which they suggested me to pay the bill amount and they will take care. I did that. I came yto London on 18th Sep 2011 and since then I stopped the service. But Bills kept on coming for me and in April all of a sudden i got a mail stating I will have to pay 2126.16. First I suggested I will not pay, but then after some time thought I will pay and asked them to stop the service and this time I sent multiple mails asking for stopping service and I suggested I will not be paying for the service which I am not using for. Now I am getting one more similar mail stating I need to pay 1800 otherwise they will take legal action. They are harassing me like this and taking out money from my side. Could you please help. I am not using this service from 18th Sep 2011, but I am made to pay for it and like this they are cheating. I have all the mails that I have asked them to stop service. Can this be taken seriously.I can forward the mails that I had asked them to stop service.Here I am not able to upload the same.

Thanks,
Vishwanath