Landing page
A single page built to get the visitor to do one specific thing, almost always call.
The difference from a regular site is that a site has a menu and sections so people browse, and a landing page removes the menu on purpose so they do not.
For a service business a landing page usually beats a five-section site, because someone looking for a plumber at eleven at night is not reading your company history.
You can tell a landing page is built right when the phone number is visible without scrolling, the text names the trade and the city in the first line, and there is proof of real work before anything is asked for.
What to do about it
Open your site on a phone and count the seconds until you find your number. Past three, that is your problem.
Other words about the same thing