How can i leagaly get serving letter if i have absconded

How can i leagaly get serving letter if i have absconded. Hi all i hve joined a blooming startup pre covid and got hired as a devloper and they put me into sales first to understand their product as a pre training.

Nearly 1 yr i was still at sales and got to know i have been scammed i absconded. Now the hr are playing around not letting me have my service letter even i asked them to pay my notice period price yet they are taking it personal. ANY SUGGESTIONS!!!