Harassment after Debt is Paid

After moving to a new home, my T-Mobile cell did not work at my residence.  I attempted to get T-Mobile to waive the $200/phone cancellation.  I went with Verizon as THEY had enough cell towers for the cell phone to work.  I finally paid the $400 to RPM and gave them permission to take it from my checking account.  Instead of taking it once, they took it twice.  Since I check my account daily, I found the second debit and contacted my bank who put the money for the duplicate payment back into my account.  The bank has confirmed that RPM was paid $400 as the transactions are ACH transactions.  They are still hounding me, stating that I have not paid the debt.  I've received collection notices and call my home constantly.  I will be reporting this to the Attorney General's Office.