1. read your purchase agreement first and see any clause about the deposit. So you know where you are standing now.
2. Call a couple of lawyers and tell them about your case and try to get a sense of where you are standing.
3. Some lawyers offer half an hour free consultation to attract new clients. If it is a simple case, they may give you answers right away.
4. Or you can buy 15-30 minutes of their time.
5. Or contact consumer protection organization.
6. Or wait for the other people here who have similar experience.
7. Or look into small claim court and get the procedures. It should be straight forward.