Sent to collections

[entigeress]

I lived in colorado. My son was mailed a written agreement from his chiropractor medical biller stating that his chiropractor agrees to the payment of $100 per month till debt is paid in full. And if at anytime he should missed a payment it would be sent to collections and payment was due the 1st of every month up until the 5th day of every month. The agreement was signed by his medical biller with the chiropractor knowledge of it stated in the letter.
the medical biller received the 1st check two days before due date. medical biller then turn around and called my son and informed him that chiropractor wasn't going to honor this agreement because it wasn't signed by him because he was mad that my son turn his name in to the chiropractor board for his billing ethics which my son has the right to due if he feels being charge unfairly. This all came about from auto accident that my son was involved in. My son was being charged low when the chiropractor thought my son was going to get money from the accident when chiropractor found out he wasn't then he was being billed very high charges to be seen. He is just graduating from college and his credit report is cleaned this chiropractor behavior will hurt my son credit

My question is :
1. Can this be true of what she (med biller) is saying that the chiropractor didn't signed it so therefore its not binding?

2. Do he have a leg to stand on in court with this written agreement ?

Thanks for your time in reading and any help would be grateful
sincerely Maria

Yes go to court. The doctor presumably had authorized the biller and so he is bound.