Keep getting the run around on my Invisalign treatment, looking for advice/refund

I started Invisalign in June of 2015. I was told I was the perfect candidate and my case was minor. The treatment should have ended that December. I have been switched from dentist to dentist 4 times by my provider, I have been through 4 sets of impressions/trays, with no end in sight. The trays are just not working the way they were promised. Is there ANY way I can get a refund for this? I feel like I paid $4000 for a service that over promised and has underdelivered for 2 years now.