You can change the freeze response. Any therapist who says you can't, just doesn't know how... as that is exactly what military training accomplishes... they change the freeze response to fight or flight, depending on what is required under the situation, even though bullets or bombs are coming at you.
It is a behavioural therapy that you accomplish by repeating a behaviour over and over again, until the behaviour is so instinctual, it becomes the new "freeze" for you, which will be a cognitive process and assessment of your surroundings to either fight or flight.
A very simple explanation of this is through martial arts training. You get a person to say and even repeat the exact things said or done that make you freeze and go into tonic immobility, then with an instructor yelling in your ear, and with an already pre-planned response, you progressively will change from freeze to react. Martial arts specific training is excellent for victims to change a fear response from freeze to fight or flight.
This is the type of thing you can achieve in your home or backyard with two other people... first developing a course of action to take, one person there for nothing other than yelling at you to get you within the now to react, the other performing the event that creates the freeze response.