Last fall I loaned 2 friends money. They were starting a gallery together and so we drafted an agreement and the three of us signed it. I was to be paid back by February 2011. I have not been paid back and the two friends no longer work together. They agreed to split the debt to me, however, one of them now refuses to pay. He is still the owner of the business and LLC but claims that he doesn't have to pay me. I believe he does because even though it was not a notarized contract it is a signed document and he is still the proprietor of the organization. What do I need to do?