Joining a new employer while cancellation papers are not issued after resignation

I am employed on an unlimited contract with my current employer. It is 1 month for the notice period (as per the labor contract).

I got an offer from a new employer and, therefore, resigned a month ago. Now, one month has passed since my resignation but the employer is not canceling my visa and wants to extend more.

Kindly advise on what I should do now since my new employer sends a labor offer and is asking for my canceling papers.