Companies asking for immediate joining

In the last 3 months I have been continuously applying for the jobs , I am getting calls in return but they are looking for immediate joining How to handle such situations.

If I say ,yes I am available for immediate joining they say to share a screenshot of LWD .

HOW TO HANDLE THEIR THIS QUESTION. AND if I say that no ,I am not serving the notice period but will try to negotiate for 30 days with my current company,they don't agree.

Please help me with this .