The moral of the story: do not pay them before you verify their filing of your insurance claim! If you do, it is very difficult and time consuming to recover any over-payment.
I made the mistake of paying the bills whenever SimonMed asked. They filed claims with Medicare such that Medicare payments were minimal or zero. After my inquiries Medicare reviewed the claims and payed their part. The result: I over-payed SimonMed more than $800 - they recognized this debt but for 2 month I am unable to get any refund. Every time I call the answer is: we are processing it and it will be another 45 days.