I had a similar experience with an ad agency that I used to do some work for (I’m an illustrator). There was an art director who pulled similar shenanigans. I later learned he was in the middle of a divorce and screwing up everything he touched. I talked to the CD, who decided to work with me directly, and things went smoothly after that. Perhaps ther is someone else at this firm that you can actually work with, rather than lose the client.
Bob Dawson