Mahanagar Telephone Nigam [MTNL] — Complain unattended

Address:

New Delhi, Delhi, 110017

I am using MTNL Landline telephone from since 3 year approx. in my
office GEETA FOREX PVT LTD located in hno 190 hauz rani malviya nagar
opposite max hospital saket. Since 2 months i am continuously
complaining for my landline telephone instrument fault bearing
telephone number 26673712 but till now no action is been taken. One
time the service man has also came but he didn't took any step to
rectify it and instead asked us to go to the main office to change it as it is not his responsibility..
As i know that he is only responsible for getting the instrument change but
he is now not even turning up to our call to address complain.
Moreover nobody from customer care support are helping us for the
fault.I had complained earlier 20 30 times but nothing happen after
that.I want to know whether my complain will be addressed or not . I am regularly paying full bill amount and service tax so i think i should get full service. but i am NOT . How
much time i have to wait for it 20 to 30 years for it ? . My whole work is
suffering because of the fault, most of my important calls are missed
as i am unable to attend it.