Debts and Credit

I lived in NY until 2009. I live in Hawaii now. On my credit report a company is saying I owe $1500 in old NY vet bill. The vet gave me a letter that says it is paid and no collection was made. The company is nasty and supplied no documentation but still hitting my credit report only through experience. How do I handle this?

Is a Promissory Note legally binding in Florida with only the signature of the payee and is a photo copy of the note valid ?

When I was married to his mother from 2000-2005, I became a co-signor to my step son's several private college loans with totaling approximately $125,000. He graduated 3 years ago and since has barely made payments. He has been late so many times that my credit has suffered and now it looks like he will default. I have the funds to keep current but I do not feel I will be paid back. His mother says she will sign a promissory note for any and all payments I am forced to make on his behalf. I would like that secured with a lean on her house. However, times being what they are, I think she owes more on the house than she has in equity. Do you have any suggestions how I may protect myself from losing $125,000? The son lives in California and his mother lives in Georgia. The bank is unwilling to exchange her for me as a consignor. I need an answer within a couple of days please.

Do promissory notes have to be witnessed and notarized in New Mexico?

My sons credit report states that he has an unpaid credit card balance of 4000.00. After research we discovered that when he was 16 his daddy requested an additional card on his credit card account with my sons name on it so he could purchase gas. His daddy had defaulted on this account. Since my son was underage and did not sign anything can the collection agency do this.