My vehicle is being repaired in an auto shop and they promised it will be done next week 10 times already, it has been 3 months!

I have a 2007 Subaru Wrx that has a blown engine. I took it to Top Level Performance for a simple rebuild and it has been 3 months already. They told me it would only take 2 weeks the first time, and the price agreed was $4,600 for everything. After the first two weeks, no phone call nothing. I had to call and the owner told me he needs more money. Having the car towed there, I just agreed to the $5,500 new total. Week after week turned into months after months. They keep telling me the car would be ready. It has been 3 months and it is still in the shop. I called 3 other performance shops and it only takes at most 2 weeks to do the job. I already left a $2,000 cash deposit with them and my vehicle is still there. This car belongs to me and my brother who is in the air force. what can i do