Global Upside - Full and final salary not paid by the previous employer

I resigned from Global Upside, Noida on **-**-**** on medical ground. I have been diagnosed with kidney disease, high blood pressure and electrolytes imbalance and hospitalized for the first time on *nd April ****. Subsequently, I was hospitalised * more times as my condition worsened periodically. For one and a half month, I kept updating the management and HR about my health status. The senior manager HR asked for my medical reports which sent via email on **th April.
Later, after my resignation, the senior manager HR called me on **th May and asked to return the laptop via FedEx and mentioned that after receiving the laptop, they will initiate my due salary and issue my experience letter. I sent the laptop via FedEx on **th May and confirmed via email. After sending back the laptop, I have done several follow-ups the company sent me Rs. *,*** as FnF amount. I am supposed to get ** days salary:
The breakdown is below:
**, **, ** March - Full day
** March - Half day
Earned Leave - *.* days
**,***/** = Rs. *,*** per day
Total ** days salary = Rs. **,***
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Please send legal notice to the company. If you get me the full amount take whatever fees need from that. But I need legal action. My question is can they hold because I could not serve their ** days notice period? I could not do so due to my health. Awaiting reply.