Tech Mahindra — negative payment settlement done but yet not acknowledged since 9 months and more

While parting from the company i was told to make a payment (8547/-) via a demand draft to be couriered to the company.

I did that. The web site to record the details was not working and so have emailed the concerned folks many times.

They keep sending me notices. Today i have received a legal notice.

Since they don't pick up the phone, respond to my email communications and keep sending me legal notices, this constitutes -
1. Harassment
2. Wastage of my time

My details
Id - 502368
Tech mahindra reference - tech mahindra/839/2018/502368
Name - jatin sutaria
Date when demand draft send - 20/03/2018

Kindly let me know the course of action