Myob closing two invoices when only one payment received

I need HELP, I have had this happen to me a few times now THAT I KNOW OF and I don't know how much money I have lost!!!!!  That has not been paid to me when I have told the client I invoiced that it has.

I am going to try to make this simple.

I invoiced monthly.  Sometimes the client has one outstanding invoice with another one due, so two invoices for the same client, same amount.

So the client pays the first invoice by credit card, say on the 17th of the month, I receive an email to say the client has paid, PERFECT SO FAR.  So myob immediately closes the invoice PERFECT SO FAR.  So on the 20th the money for that invoice goes into my bank account - HERE IS THE PROBLEM - the bank feed receives the amount and automatically closes invoice 2.  So two invoices closed but only one amount received.

So the client rings me and says I owe you for an invoice, I look on system and I tell them IT HAS BEEN PAID, they disagree!  I look on system and I tell them they paid one invoice on the 17th and one invoice on the 20th.  IN FACT NOT CORRECT, the system has allocated it twice, once when paid by credit card and then AGAIN when the money hits my bank feeds.  HOW MUCH HAVE I LOST, it was only the persistance fact that my client said it's not paid AND HE WAS CORRECT.

HELP

Teena