Product: Debt collection

My wife and I cosigned a XXXX XXXX Credit Card for our son and his wife. The kids fell behind financially and were unable to make their payments but did not notify us of their situation. Before we could remedy the situation, we were sent to collections ( Suttell, Hammer & XXXX ). 
My wife coordinated with the collection agency who and where to make payments to. In fact, she was told to send the first two payments by physical check to the address to ensure everything was setup correctly and the client was receiving the money. After that was confirmed, she was told she could now setup electronic payments, which she did. Electronic payments were made faithfully every month to the same address as the first two physical check payments. All payments were being negotiated because our bank statements were showing they had gone through. 
We were recently notified by Suttell, Hammer & XXXX Attorney 's that we owed XXXX in full for an outstanding judgment. We were shocked to hear this since we had paid over {$4000.00} since first receiving the judgment against us. We sent all records of electronic payments to Suttell, Hammer & XXXX to show we had more than paid the original judgment amount. They were unable to find any record of our payments and said there was no account showing any payments were made other than the first two physical check payments. 
We were told that we must have sent the electronic payments to the wrong address. However, we have proven that the address is correct because they received the first two payments correctly. We were not notified to send payments to any other address. We have spent weeks communicating with Suttell , Hammer & XXXX and showing them documentation of electronic payments being made. They continued to deny our proof and continued to state there was no account showing payments had been made. 
Finally, Suttell, Hammer & XXXX were able to locate our payments informing us that they had been going to a XXXX XXXX account. XXXX XXXX did not know what the payments were for and were supposedly sending us the money back. We never received any money and therefore did not cash any checks. We were never notified by XXXX XXXX that they had been receiving money from us and that they were putting it in some kind of account. 
Now, having proof that we had actually been making the payments because XXXX XXXX has admitted they had received all payments, Suttell, Hammer & XXXX has finally agreed that we had been making the payments and have satisfied the judgment but their client ( XXXX ) has not received anything from us so it is our responsibility to pay them off. We have refused to get involved between XXXX XXXX and XXXX because it is Suttell, Hammer & XXXX responsibility to satisfy the judgment, provide us with a receipt of payment in full, and file the satisfied judgment with the court. 
The latest correspondence with Suttell, Hammer & XXXX was an e-mail from XXXX telling us that XXXX XXXX will refund us all the money we have paid and then we should pay XXXX. We are concerned that the judgement will not show satisfied on the date we completed our payments but rather they will try to show it satisfied when they receive the whole lump sum. This would negatively affect our credit rating, causing us difficulty in obtaining financing for a new home.