Jay A Hollander Inc

I went to Dr. Hollander for small work when I first moved here. Went back a yr later for bigger work and was told I had a $15 credit they never told me about. Was also told my work would be covered by my Ins. They charged above and beyond what was covered, so I ended up owing them $900! I pd. then they said I still owed $20 for mouthwash. I sent them $1 that they accepted for payment of debt and said that would be all. They sent me to collection for the supposed $19 I still owed. Now I have a collection on my credit for $55 from them. Luckily I have their unprofessional letters to show whomever I need to prove the collection is not worth anything and that's why I refuse to pay it.