Hospital outpatient clinic charging me for a service they didn’t perform

My daughter fell as she was playing basketball and had a minor fracture on her wrist. The urgent care took an xray ant then put her a splint, but they told us to followup with an orthopedic.

We then went to the clinic in question after one week. The doctor reviewed the xrays we had already, and touched her wrist to see if she has any pain, and then gave us another type of splint for her to wear for the next 4 weeks.

We were surprised when we received the bill from the clinic. They charged us $250 for CPT code 99203 (outpatient visit) and $850 for CPT code 25600 (closed treatment of fracture). I found out that this was based on the visit notes the doctor made, who wrote “Immobilization: Closed treatment with an Exos brace”. However, her notes are wrong since no treatment was done.

I asked the clinic to correct the notes and send it to the billing so they can remove the CPT code 25600, however it’s been 3 months and they still haven’t done anything despite my followups (both in writing through their portal and over the phone). They now sent me a final notice to pay $1.1K (my plan has a high deductible) and threatening for collections in 20 days.

What are my options? I don’t want this story to have any impact on me before it gets resolved as I believe it is their error.