Hi Weecalf,
The only`phone number I have is 03002003310, which is self assessment.
The letter I had also stated I owe £4.20 and to log on to the website and click "view statements", but when I did, there was nothing to click on. Tried their "search" box and it took me to a page which had nothing to do with statements.
I`ve had so much trouble with the GOV.UK sites with various ID numbers and passwords that I`m considering using (after training) using carrier pigeons in future, to save on the cost of postage. Afer all, it does not cost the staff of HMRC to write to me, they just send it to the post room and somebody franks it eventually.
If you can get on to www.gov.uk then go to the very foot of the page under "contact" you might be very lucky to send an email complaining about their site.