This is bloody height of irresponsibility.

I asked the customer care and Nethra (from TATA, she called me one
day) that who would pay tthis month rental when consistently I am
getting 200Kbps speed whereas I have 750Kbps unlimited plan. She told
me she would get back to me after some time, but no body called me.
Every day some or the other Tataindicom's irresponsible executive
calls me, listens entire story and cuts the call. Problem is still the
same.

I have full proofs (screenshots and emails), so believe me I am not
going to pay you single penny this month. DO whatever you can do.

And REVERT MY PLAN TO PREVIOUS ONE i.e., 128 Kbps unlimited or
TERMINATE YOU USELESS CONNECTION.