The companies who agreed to pay the settlement to 317 people were MyMedicalLoan.com, a California entity which did business as Surgeryloan.com; another California company named Duvera Billing Services; Colorado-based Highlands Premier Acceptance and Paramount Capital Group, which is based in Pennsylvania, according to Schneiderman's office.
In addition to the $230,000 in repayments or credits they agreed to pay, the companies also will collectively pay $35,000 in penalties.
Read MoreStates made 'little progress' in health
MyMedicalLoan.com, Duvera Billing and Highlands Premier did not respond to CNBC's requests for comment.
Paramount Capital, in a statement released Thursday, said that it had from 2009 to 2013 purchased retail installment contracts from MyMedicalloan and because that company "is a California corporation . . .we understood our licensing requirements to be regulated by California, not the State of New York."
"Upon receiving notice from the New York Health Care Bureau of their investigation, we immediately pledged our full and complete cooperation with the New York attorney general and today's settlement agreement, which includes minor penalties for Paramount, is a reflection of that cooperation," Paramount said. "We want our customers to know that no APR exceeded 17.99 percent on the contracts we purchased from [MyMedicalloan] We have already reduced that rate to 16 percent and will make retroactive interest refund payments to all affected borrowers well within the 90-day agreement reached with the New York attorney general."
"Furthermore, Paramount will be contacting each affected borrower individually to explain the mistake, offer our sincere apology for this oversight, and to notify them of the interest due each of them."
The case was spurred by a complaint filed with the attorney general's office in 2012, by a 50-year-old mental health counselor from Yonkers, N.Y., named Karen Brandon, official said.
Brandon told CNBC that in 2011 she had financed a tummy tuck procedure with a loan she arranged after first contacting the online broker Surgeryloan.com, which had been recommended to her by the office of the doctor she expected to perform the operation.
She said she signed an agreement to borrow a total of $8,000—and paid another $3,000 directly to the doctor who ended up doing the tummy tuck. A month after her surgery, in April 2011, the lender began taking $365 in monthly repayments directly from her bank account, as agreed, Brandon said.
Read MoreObamacare fees OK, consumers say: Survey
But more than a year later, after having paid a total of $5,600 on the loan so far, Brandon contacted the lender to notify them that she wanted to pay off what she owed, because she was obtaining another loan from her bank for that purpose.
An employee of the lender then claimed that she now owed a total of $19,000 in principal and interest because she had borrowed $12,000—not the $8,000 that was stated on her loan agreement, Brandon recalled.