Yes, if there was a clear breach of ethics which caused be harm and I couldn't resolve it with the T directly I absolutely would complain to their registering body. The reason being that Ts work with very vulnerable people at times and it's important they are ethical in their work, be complaining may save someone else from a bad experience but it would also be part of me respecting myself. It matters if someone treats me badly and that needs to be addressed because I'm worthy of receiving professional, ethical care from the people I employ.