Tata Docomo — Got bill despite deactivating the device

Address:

Tamil Nadu

I deactivated my tata photon data card on 13/6, after paying the last of my dues on 12/6. I was told by the tata contact rep that the device will be disconnected and I will have to pay only 7 days rent. She informed me that I will get a email asking me to pay forthe 7 days, I agreed.
By the end of the month I am getting a whole month's due of Rs. 805! How can that we be possible if the device has been deactivated?
I went back to the Tata contact shop, and the rep informed me that the device has been cancelled according to her computer on the 13th of June.
This is crazy! I am getting repeated messages and smses asking me to pay or face legal action, can you believe this.
They are making a mistake and we have to pay?
I have been trying to email them, no response. I am trying to call them, a girl picks up and without asking any information from me she says she will check and get back!

TATA HAS THE WORST SERVICE AND CUSTOMER SERVICE.

Details for my photon card deactivation.

I cancelled on 13/6
> My Request No. is[protected]
> Account No.[protected]
> Photon No. [protected].

Please ask these people to stop asking me to pay for services I cancelled long back and which I did not use.