Your insurance company sends you an Explanation of Benefits (EOB) for every claim that they receive. Those are important documents - 1) it helps you make sure that the bills you receive from your doctors are accurate and 2) if a claim goes through for services you never received, then you can notify your insurance company. Every insurer's EOB has a phone number listed on it - sometimes they even have a separate fraud and abuse prevention #.
If you don't pay attention to your EOBs when they come in the mail, you can always call your insurance company - they can either reprint your EOBs, print a report for you showing what claims have come through under your account, or verbally review them with you on the phone. Also, many insurers have an option where you can register on their website and see claims processed under your policy.
There are definitely many options where you can confirm what has been billed on your family's behalf to your insurer. Definitely let your insurer know if your provider is billing for services you/your child never received. Billing fraud drives up the cost of care for everyone. Its only a small minority of providers who are unethical enough to deliberately fabricate services to bill, but those who do that sort of thing unfortunately contribute to driving up the cost of care for everyone.
15 years working for medical providers, health insurance companies, and employee benefits