Auto Insurance Claims: Fraudulent car repairs, salvage yard, auto repair shop

Question
What do I do if I have 100% positive proof that an auto repair shop did not replace the part that they were suppose to replace. I will add they have already billed the insurance company for the work "not" done. To explain a little, I was rear ended while driving my older vehicle. Due to the age the other guys insurance company said they could only replace it with a used part, which I was willing to accept if it worked properly. After so called repairs at the shop that the insurance company told me to go to, I noticed it still did the same thing (broken steering column) I was told that was the best used part they could find. Since it was a steering column, I was told to get rid of my old keys they would give me a new set. After "repairs" I decided it was too similar to my old steering column and tried the spare key I still had...perfect match. So the following day I went back to the repair shop and asked for my old steering column, which they gave to me. I took it immediately to my repair shop that I usually use and they confirmed...the column that I picked up was a salvage part, still had the salvage markings and the key was different than my spare key. He even called the local salvage yard and confirmed that was the part they sold to the shop that did the "repairs".He also looked at my steering column which was still covered in dust and grease from years of being there, also the bolt that holds the steering column on was never touched with a socket or anything(still rusty and covered in grease etc) I just don't know where to go from here. I don't trust that shop to do the repairs, and I feel that they should pay for intentionally frauding me and the insurance company.

Answer
You will need to be prepared to obtain the proof that would be admissible in a court of law that the shop actually profited additionally by using the alternate repair method.  From your long and involved story, I seriously doubt that this is the case.  In fact, it sounds like the likely lost money on the deal considering the cost of time.

The fact that an insurance company was "willing" to pay for a steering column on a rear end collision sounds pretty hokey to start with.