Tata Indicom — incorrect bill

Address:

New Delhi, Delhi, 110046

I was contacted by airtel support for changing and moving the subscription from tata to airtel, given tata were supposed to shut down the service in the month of april. I agreed to that and as per the process the airtel support took the tata photon dongal from me and provided me with airtel device - per my understanding, given i am not in possession of the device and its with airtel support it is upto airtel and tata to make sure that the service for tata be immediately stopped and not charge me from that day onwards i. E. 11 march 2018.

However, to my dismay i have billed not only for tata service but airtel as well - not sure why i need to pay for both???

Also, even after my repeated emails to them ; there were no reply or explanation on the incorrect bill - expect for the automated response and what amount was due.
Even during the calls i got from tata indicom - there were no answer to my queries except that they would discount the pending amount.