Former Employer Wants Compensation a Year After I Quit on Day One—What Should I Do?

I joined a corporation last year and had to quit on the first day due to certain medical conditions. I informed the concerned HR about this on the same day. However, now, almost a year later, they are demanding that I pay compensation for leaving without serving the notice period, even though I only worked for one day and was on probation at the time.

At the time of my voluntary abandonment of service, I asked the HR if anything needed to be done on my part, and he informed me that there was no such requirement.

What should I do?

Have they given anything in writing? Please share correspondence duly masking names, etc. They have no chance of winning any legal battle on this ground.

Yes, they sent me a letter detailing the amount of compensation due. Additionally, they opened a bank account in my name even after I informed them that I would not be joining the company after the second day. They credited a certain amount to this account, but I have no authority over it and possess no related paperwork. The bank in question is a leading private bank.

It was part of the first-day formalities to open the salary account, but I informed the concerned HR about it at the time of leaving. Moreover, I received the account opening message on my phone number months later.

Additionally, I have not used this bank account nor have I received any passbook or any such papers relating to that account.