Big Boys Tires & Auto Repair

I took my car to big boys for a certain reason which was the rack and pinion because it was super hard to turn the wheel. I told them the problem and they said it would be about $800 to fix it well when it was done they charged me over $2,000, They put way more stuff on it then I asked them to I only asked them to fix the rack and pinion. Well I looked at my receipt and it says about 10 other things on there including the drain pan and oil filter. Now its been about a month since I got my car back from them. I was driving to the mountains and my car starts making a knocking noise I talked to a different mechanic about that and he says I have been driving my car with no oil, which I had just got an oil change about 2-3 weeks before I took it to big boys, meaning that when they changed my drain pan without my consent they also did not refill it with oil, now I have to get a new engine cause mine is knocking. I dont have the money to do so, because I paid over $2,000 for them to fix my car which they actually just messed up and the reason I took it there didnt get resolved it is still very hard to turn. I would really appreciate it if you guys can help me get my money back I paid over $2,000 for them to just mess my car up more.