GOV.UK does not have a phone number for individuals asking specifically about the UK government’s website. If you need to contact a specific department please navigate to GOV.UK’s general contact page: https://www.gov.uk/contact
If your enquiry concerns the website itself, or a fault or a problem you have encountered, seek support using GOV.UK’s form: https://www.gov.uk/contact/govuk
GOV.UK is the UK government’s website which lists the major services and departments of the British government as well as contact details therein. It was conceived as a unified replacement to existing government websites.