I don't know if I would do either - contact a lawyer or let it go completely. I would re-listen to the recording (if possible) and confirm there was not a disclosure that I missed. I would contact the MSC and if they provide no assistance, then I would probably contact a credit bureau (there are 3 credit bureaus in the US - Experian, Equifax, Transunion). I believe within their tools you can try to dispute the opening of the credit line.