I received a collection from a dentist I had seen in 2005. Here is the thing, in 2005 I already had a medical savings account from my job, and I had paid with the Visa card that was linked to the account. So, I knew I had paid the balance in full. The dentist office never posted the payment to the account and sent it to collections... I had to get a letter from the Visa company saying that the amount had posted in 2005, and then send it to the dentist and to the collection company. I was soooooo mad!
So, get proof that this is your account, detailed proof of the original date you were, what you signed, etc... just a statement is not enough.
Good luck!