What are my options when dealing with mechanic who didn't correctly repair my car?

I took my 2007 Camry in to a mechanic 2 weeks ago with Engine Code P0301, misfire cylinder 1. The mechanic still ran diagnostics for $100 and then did a tune up replacing all plugs and coils. After driving less than 200 miles, the light came on again with the same error code...the performance was sluggish as... show more I took my 2007 Camry in to a mechanic 2 weeks ago with Engine Code P0301, misfire cylinder 1. The mechanic still ran diagnostics for $100 and then did a tune up replacing all plugs and coils. After driving less than 200 miles, the light came on again with the same error code...the performance was sluggish as well. So naturally, I call them and take the car back.

Now they want to charge me again for a diagnostic, even though it's the same code and they just did this 2 weeks ago. I think that's absurd...frankly I don't think they should charge me a nickel for fixing anything that they fixed 2 weeks ago.

So here's my question...what recourse do I have? I know a few places who can diagnose for free, but if I ultimately still need to get the plugs and coils replaced again, I feel this place should do it since I already paid. Their warranty for parts and labor says 24,000 miles/2 years. Of course I'm now afraid they're going to blame something else for the code.

Other than finding a new mechanic after this, what advice would you give on how to handle this. I don't want to give this place anymore money, and I don't want to 'void' any warranty but having somewhere else diagnose it.
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