2006 Chevy Silverado Whinning noise when turning to the lef

The Brake booster in my truck failed to weeks ago, I had the car towed to a GM dealer, since it was under warrenty, when I picked up the car, I learened that they also replaced the intermediate shaft in the steering column, when I asked why they said that it was worn out. That same day while driving, I began to hear a squealing noise whenever I turned left, I brought the truck back and they said it was the power steering pump, they took the truck and in two hours they told me they replaced the pump, and it fixed the noise, after I took the truck the noise came back that night, my warrenty is covering this but it is a hassle to bring the truck back every week, please help if you think you know what the problem is. The Truck is currently in the dealership again, for the same thing are they doing something wrong or, are they misdiagnosing the problem