i was a this hospital a year a ago for a back pain...

i was a this hospital a year a ago for a back pain..
they send me a bill of 3,479.16$ for a shot!
i was really surprised about the price but i want to pay it i do not want any problem! i called them and they said you can pay with payment or you can pay one time with 20% discount i said ok i will pay one time with 20% discount so i pay 2,783.33$!!!!! now after 6 month they send me a collection that i own them 695.83$ the same 20% i got discount because i paid the 2,783.33$. i called them they said no one say something like that talk with the collection company and hang up on me!!!! i'm taking a lawyer to sue this hospital for this scam!!! do not go to this place it is a scam!!!