Account in arrears but paid up

Received email from debt collector regarding my account that is in arrears, I phone payflex they gave me the order number that they say the amount is in default, I went to check on my email, I received an email confirming that they received the payment with the same amount and same order number. Now they say that I reverse the payment. How do you do cause I know that you can only reverse a some debit order but not an online transaction. Now no one can help me all I get when I post my complaint I get insulted from the customer service telling how I’m such a bad payer and how my credit score is so low. Now how do we solve this. You can not say I owe something while I have proof that this was debited even have a confirmation email from them with the amount and same order number