Adjustment of Status - I-485

I have a friend who is in this situation and I need your advise on what to do:

"My wife applied for a B2 (medical) visa on the 23rd of October 2017 stating her intention to give birth in the United State of America and she was given a two years visa. On the 5th of December 2017, she gave birth to our daughter at a Medical center in Texas.
 Upon her discharge in December 2017, she was billed $2,900 for hospital and lab, $2,500 for her Obstetrics &Gynecologist and $960 for my baby's pediatrician which I paid in full and was issued a receipt and a zero balance stating that I have paid all bills in full and the state of Texas nor any other government institution did not make nor is set to make any payment on her behalf.
 On the 4th of December, 2017, I applied for a B1/B2 and stated that I was going to see my wife because the doc needed me to sign some documents and I was granted the visa.
I came to sign all necessary documents and returned back to my country with my wife in the same month of December 2017
 On the 5th march,2019 we applied for a B1/B2 visa for my 2 other daughters with the intention of visiting Florida for a vacation in August 2019.
Unfortunately for us, they were denied the B1/B2 visa and the Visa Officer explained to me that I was under billed hence didn't pay the complete medical bill for the birth of our baby in 2017 even if I had my receipt and zero balance which stated clearly that I wasn't owing. She furthered explained that the hospital might not own up to this,they are into some forms of fraudulent deals. All they do is to hide the real amount for birthing from their clients then go further to collect the balance from the government unknown to the clients."

Guys, what can we do in this situation