Aspen Dental

My account was paid off and then I receive a bill for $427.00. My balance was zero. Almost a year later they send me a bill for $427. They indicate the insurance company did not pay them. A year later??? I also have asked for a complete breakdown of all payments made including my out of pocket payments which total $1089.00. I want a complete breakdown of what was billed to the insurance company( I want the address to where they submitted the bills to the ins carrier), what was paid by the insurance carrier and what I paid. I find it rather odd that a year later they are sending me a bill when the balance was zero a year ago.