Company Asking to pay the shortfall of Notice Period When am ready to serve the Notice Period

I joined a company and worked for one week, but during the second week, I was hospitalized for four days and did not inform my employer. When I returned, I immediately submitted my resignation and informed my employer that I was willing to serve the full notice period. While I was hospitalized for four days, it caused damage to the project, and the client imposed a fine on my employer. I asked my employer to show me the details of this fine, but they did not provide them. I had not received any client credentials and had only attended one client meeting. Despite this, they removed all my credentials, claiming that I had absconded from work, and my resignation was not accepted. Later, I went to the office to discuss the situation with HR. They stated that due to my absence for four days, which led to the client imposing a fine, they did not want to allow me to serve the notice period. Instead, they asked me to write an email and a handwritten note requesting a reduction in my notice period (shortfall of notice) and to pay for this shortfall, which is against my willingness to serve the full notice period. Now, my employer is forcing me to pay for the shortfall of notice to be relieved from my current position. It has been one month, and I have not received any official confirmation about the acceptance of my resignation. They are simply holding me without releasing me from the company, and my provident fund is still active.