Problems with mechanic

Hi All,

I believe I am being taken advantage of by a car dealership in Waterloo and I would greatly appreciate any advice. In particular, I was wondering if there are any consumer protection agencies out there for cases like this. The story is as follows:

My 2000 Nissan Sunny (diesel) was running rough and cutting out so I took it to a car dealership in Waterloo. After running diagnostics, they told me the problem was a bad injector and the price would be about 800 euros. After the staff ensured me that this was the only repair the car needed, I authorized them to carry out the work. Unfortunately after they replaced the injector, they said that the car was still not running properly and they then needed to replace the priming pump for the fuel filter (~300 euros). I reluctantly agreed after again being assured that the car would run after the part was replaced. But again, the car does not work and they say it needs a new fuel pump.

So now I'm in quite a predicament. I will not authorize any more work nor do I want to pay for any of the previous work that was unnecessarily done as this is obviously a scam. But what are my options? If I don't pay, I'm sure I wouldn't get my (broken) car back. And if I end up leaving my car there, could they sue me?

Many thanks