Backinuk

I have recently moved back to the UK after many years abroad. I completed the CF83 and got the list of years and payments I needed to make. I have made the payments but am pretty sure that I have paid into the wrong account for the Type 2 payments. Who can I contact to find out about this? I have tried the main number on my letter but the person I spoke to insisted that I should have a reference number which is not true for overseas payments. Any help much appreciated.