Dental Insurance Questionable Billing.

I have dental insurance through my union. I looked into and choose an in network provider from the insurers website. From what I understand to be in network they have agreed to the fee schedule from the insurance company.

My wife took my son in for a cleaning and to check tooth pain (turned out to be a cavity). We got a bill in the mail for what were supposed to be covered services on the providers fee schedule. They are telling me they can bill anything they like over their agreed fee schedule.

She then took my son to have the tooth extracted (baby tooth) and my daughter for a cleaning. The dentist charged her full price which she paid with her credit card and billed my insurance company.

I’ve called my union benefits rep and insurance company who both say I should have been charged nothing out of pocket. I’m calling the dentist tomorrow to ask what is going on and to request a refund of anything paid. I’m sure they won’t give it to me.

Am I correct in how that fee schedule and insurance works? Do I have any recourse here?