My vehicle is in the workshop and AA won't fix it after they have acknowledged that the turbo charger is covered for a certain amount

I have just been told by AA that the won't assist me with my mechanical warranty claim. I have consulted them notifying of my car mechanical issue. I was advised to take the car to the tax paying workshop of which I did as instructed. The turbo charger was removed as per AA instruction. Now they say they won't fix my car.