Lightning Lizard Service Center

I’ve been paying on a car from Lightning Lizard Auto Sales for about 8 months, and recently it broke down. I thought it was the timing chain, so I had it towed to their shop since that should’ve been covered under warranty. After sitting there for two weeks, they finally called and said it was ready. They told me it was just the spark plugs and charged me $300. But never once called to explain the issue or get approval before doing the work. The very next day, the check engine light came on and the car started misfiring. I took it back and told them the coil packs needed to be replaced too. They quoted me $468. I told them I had a cheaper quote elsewhere and would pick up my car. Then they tried to charge me a $105 diagnostic fee, even though I brought it in for a specific issue. I refus