My daughter received XXXX services at XXXX facility, I had paid the {$25.00} copayment. 
Insurance statements and credit card statements confirm I paid the {$25.00} copayment. 
I sent a certified mail to debt colletor with proof of payment. I kept record that letter was received by debt colletor. 
After sending the mail, debt collector keeps calling statign they have not received any certified mail, that I still how {$25.00} + interests. 
I had to sent a fax with all information again.