Resignation and no relieving letter after Maternity leave - pay recovery of notice period

I was on maternity leave and after maternity leave I was not able to join back. I resigned and they accepted.
After that when I asked for relieving letter then they said you should pay recovery notice period because you didn't serve.

Dear Madam,
Everything depends on the relevant clause relating to the notice period for resigning.
It appears you resigned immediately after your maternity leave without rendering service during the notice period and the company is right in recovering the amount towards notice period.
Regards,
Vinayak Nagarkar
HR-Consultant