Bharat Sanchar Nigam [BSNL] — Unnecessary bill of Rs 1700 on July 2020

Hereby, I, Swapan Kumar Nath, would like to inform you that I am an ex-employee of BSNL. As a part of my benefits, I was allotted a rent-free telephone (Acc. No. [protected], Customer ID. [protected], telephone no. [protected]) since BSNL was launched with 300 free calls per month. However, I do not make any calls from it as it is mostly dead.
I had a Broadband modem registered through this number, which I have surrendered on 30/7/2018 and had paid the bill of INR 673/- on 23/8/2018, according to the bill generated. After that, till June, 2020, NIL bills were generated. However, in July, 2020, a bill of INR 1770/- has been generated, demanding a one time charge of INR 1500/- with INR 270/- as the GST. As a retired BSNL employee, I feel this bill is unjustified as I enjoy a rent-free telephone. I am attaching the photos of my bill, my allocation of free phone and the complaint mail that I had sent to BSNL. Your interference is solicited