They're as bad as the CSA for getting things wrong IME.
They did this to dh. He was originally told that he had to pay x amount per month towards to costs, appealed and then had a letter saying his costs would be paid. About a year later he had a letter from them saying he owed them thousands. They denied ever sending the last letter, so we had to copy everything and send it off to them. We waited to hear but have heard nothing since and that was about 7 years ago.
Have you still got all the correspondence?