AVCO Financial Services will loan money to anyone(just pick a name)

I discoverd a loan with AVCO on my credit report that I did not make.I went to see the manager.I asked to see the loan contract.I told her the signature was not mine.I asked for a copy.She said the copy machine was not working,after discovering my ex-husbands name was also on this contract.She told me I could sue my ex.I do not think it is right for a loan company to do this.I had no knowledge of this transation.How did this happen? This all happend two years ago.I did not know what to do about it.