Online account and paper letters don't match

I have received a letter saying i owe money from a simple assessment, however, My online gateway account says I have paid the right amount of tax, and there are no messages saying I owe anything. I also spent ages last year sorting this out as you had spurious info about a second job i never had, so this is becoming irritating

Hi Markaccus,

To review this you will need to contact our Income Tax department by telephone or in writing
Income Tax: general enquiries

Thank you.