Broke and Deband

Sisters, ages 14 and 16, were treated by an orthodontist. The 16-year-old had been completed and debanded and in retainers. The 14-year-old was completed but due to a dispute over payment of the fee, the orthodontist refused to remove bands until payment was made in full. The parents had completed payment for treatment of the 16-year-old, but had an $800 balance for treatment of their younger daughter. The parents contacted the office and explained that they'd had recent financial difficulties and asked if they might make extended payments on the balance. They were informed that until the balance was paid, the orthodontist would not remove appliances. They were further informed that there would be an additional charge for retainers that must be paid in advance. The parents subsequently contacted three other orthodontists, all of whom declined to remove appliances.

Wrong doings by whom? Better ways? Why?