Need suggestions as HR is asking for documents without sending an offer letter to mail ?

Need suggestions on employers asking documents and refusing to share offer letters?

So i got an offer from a noida based company and they are asking for documents before sharing the offer of employment and when I called and asked HR to share the offer letter documents on mail HR refused saying she can't share it now as per company policy first send your documents and all then we will officially sign the offer and only i can explain you the offer and ctc breakup on call verbally.

I was thinking to use this offer letter to negotiate from future offer as I dont want to join this company because the company policy is shit they want me join on next Monday and they themselves have a notice period of three months and only 18 paid leaves and no separation of SL, CL and PL when i asked them to negotiate on that they refused saying it is what all big companies follows

What should I do, how to get an offer letter on mail or is there any way to negotiate them with notice period or hybrid working as its strict 5 days 10 to 7 in office?