Changing advocate

I approached advocate A upon getting a call from another opponent advocate X (appointed by my wife) to consult on how to go about. Advocate A said he can handle Advocate X and get this closed within no time. After couple of meeting with Advocate A for few months and paying him what he asked for then, i felt uncomfortable and un-satified so i Changed my advocate to Advocate C. After a week or so Advocate A sends me a message to pay him for 4 years services that I avalied from him? Which is a big Lie, cause i approached him just 2 months back. I need some wise and serious advice as to how to handle this Advocate A. What should I do?