[Resolved]  Reliance Communications — asking (legal action threatening) to pay broadband due of last year which was already cleared by returning modem

They are sending threatening legal action email unnecessarily. We have shut the broadband connection because of an intermittent internet connectivity last year. After that we all vacant the flat. Not a single byte we had consumed as we all vacant the flat.
After i month i got the call from one of their representative for the payment. I clearly said i will not pay as i've shut the connection and not used the internet as we vacant the flat a one or two month ago. So, they asked me to submit the modem and wire to their agent (From one whom i got the connection)
I called that agent i submitted reliance modem, wire etc.. He told me i will inform and update in the system too that you've submitted these stuff. After that you won't receive any mail or call for the payment.
Now some days back i got a mail from some agency (Fake) for legal notice of due.
I've cleared everything by submitting stuff. Now why they are asking to pay.
Pfa of the mail