NCO financial or OSI financial I paid 616.47 to NCO financial and they are saying they never received payment. i have a receipt for western union stating that I did. dont have city, Wisconsin Natonwide

I made a payment to NCO financial back in march 2009 for 616.47 through western union quick collect. I was trying to pay this off so I could register for college. I could not register until this was paid off, I had a block on my account. I sent the money quick collect  but i sent it to the wrong account number I called western union and NCO. Western union also called NCO and gave them the correct account number. It was confirmed that the money was received and the hold was taken off at the college. I registered and attended college for one quarter. Now I am trying to register in sept and I have that hold again. NCO is saying I didnt pay, that they never received the money. I sent them a receipt from western union and I also sent the college a receipt. Nothing!! I don't know what else to do NCO wont call the school to confirm that they received the money, and the school basically doesnt care because they say it's between me western union and NCO. I have the receipt saying it was paid and to whom. The lady that was helping me at NCO told me she would look into it and that she would call me back. Well this was at 9am I called back at 1pm and she was gone for the day. I need to get registered and that block wont be lifted until these people call. I am not paying them 616.47 again no way!!