How long does it take for a car repair shop to fix a problem?

I recently had new springs installed at a specialist workshop. After the key was dropped in my mailbox and I picked up the car, I noticed that the steering was creaking and that the rubber buffers and rubber spring plates hadn't been installed. I didn't receive a response either by email or by phone. So my question is, how long does a workshop have to fix their problem before I can take other steps? (Use another workshop and invoice the first one, etc.)