THIS IS NOT MY DEBTDear XXXX, Dear Billing Dept Manager, I am writing this letter to confirmed that this is not my debt. And stop contacting me. 
I do not have any responsibility for the debt but you 're trying to collect. And you did send to RPM Collector. 
I am very upset to received this notice from you and RPM Collector LLC. 
I have paid on XXXX/XXXX/2015 with total {$100.00} by my credit card XXXX at XXXX XXXX XXXX # XXXX XXXX, XXXX, CT XXXX. ( Reference receipt ). After 7 days I have received XXXX more bills, I did call to Customer Service to make sure, and the teller told me " you paid already ''. Later a week, I am still received XXXX bill and RPM Notice on XXXX/XXXX/2015. 
And I did send the letter to answer about this debt at RPM on XXXX/XXXX/2015 but I am still received another letter to collect money from RPM again on XXXX/XXXX/2015. 
So I need you have to verify with your Billing department 's XXXX about this problem. 
If you have good reason to believe that I am responsible for this debt, mail me the documents that make you believe that. 
Stop all other communication with me and with this address, and record that I dispute having any obligation for this debt. 
If you stop your collection of this debt, and forward or return it to another company, please indicate to them that it is disputed. 
If you report it to a credit bureau ( or have already done so ), also report that the debt is disputed. 
Thank you for your help, Sincerely,