I don't know if you would want to bring this to court - I suppose that depends on how many hours you put into this and what it is worth to you. 9 months is a long time to let this situation drag on. I think that you need to try and meet up with your client in person, even if that means going to his/her house and discuss the matter. Clearly they are trying to get out of paying, but before you put yourself and the client through a lawsuit I would try and settle it between the two of you.
Next time, if it is possible, ask for a down payment or pay in advance. If you are working for a legitimate company, where there is trust in your work, then this should not be a problem.