Reliving letter not issuing - absconding

Hello sir, This is pushpendra . I have been employed in a private company from 13 nov 2017 to 23 march 2018. This was my probation period . Under probation period notice period is of 15 days. I have formally dropped an email on 8th march 2018 to my manage , hr manager , and business manager stating my leaving date to be 23rd march 2018. And I left organisation on 20th March 2018 , 3 days before my leaving date due to some medical emergency. Which I told to my manager verbally. On 25th april 2018 company dropped an email that I am not coming to duty and need to report in 2 days. To which I replied that I have dropped resignation and informed. After that there is no communication. I require reliving letter and they are denying and saying you have not resigned. As per company email I was present till 20th match 2018. Still they are not giving letter and threatning me. Saying company had no liability after 2 years to keep record. Please suggest is it my fault. Or how can I take my reliving letter.