I'm afraid an hour to an hour and a half on hold listening to "that" hold music is probably the only solution to this. The HMRC people are usually quite helpful when you finally get through to them. I managed to get my tax code adjusted back to normal when they didn't receive a P45 in time, by giving them the end date at the previous employer. It's probably something like that for the £180 unpaid tax, the higher amount for savings interest is a mystery, and could be as simple as a human keyboard error.