I came to USA with company A. Company A got merged with company B, so I started getting paystubs from company B. Now after working for more then one year I got an offer from company C, company C filed H1B
transfer and sent me case number after which I resigned from my previous employer (Company A/ Company B) and joined company C. Now USCIS is asking more information about my case. They are asking for I797 from company B. I dont have any I797 from company B as it was just a merger and not company change. Company B is not responding for my calls as they didn't pay my last three weeks pay.
Now USCIS has requested more information and Company C is asking me to provide some kind of merger proof (Merger successor or any press release). Company C says without merger proof there are good chances of H1 transfer
will be denied and I will have to go back to my country. I have only email, All the paystubs (From company A and B) and documents (Not signed) which were sent to us by priority mail to sign and send it to them back. The main
page announces merger but there is no signature.

Please advice what I should do ? Is this my responsibility to get merger successor or effidevit of the merger from company A/B ? If yes they are not responding to me and how can I force them ?

Your response will be greatly appreciated.
Thank you