Appleplex

Hi, To complete my tax form I am asked to verify that the underpaid tax from a previous year is£0, by checking this against my PAYE Coding Notice. However, I have been sent no such notice; nor can I find a copy of it in the HMRC personal tax website. The link to contact HMRC provided here takes me to a page where the phone number provided is NOT for tax affairs, it says; but the link to the tax line takes me in a loop back to the start. I am therefore unable to contact HMRC to verify the question on my tax return. - Is this the correct number 0300 2000 3300? - Is there a way to view the P2 notice which I have not received in the post? I am reluctant to simply confirm the amount is £0 without seeing the Notice, even though it is no doubt correct. (The P2 seems to relate to a recent change of employer for low income part time work). Thank you.