I have been paying on my medical bills regularly and was sent to collections anyway. Is that legal?

We incurred large medical bills and tried to set up payment arrangements with Novant health. The only option they would offer is to charge us 12% interest on the balance if we couldn't pay it in full in 60 days. If we do not pay in full in 60 days, they will take us to collections. If we are making reasonable payments every 30 days on the medical bills and they take us to collections, how will that affect our credit?