At any time surfed for the amount of a pizza place on your iPhone and just wanted to switch the telephone number straight from the webpage?
If you are using the standard browser on your iphone, which is Safari, which no issue at all.
Firefox automatically converts numbers that look like telephone numbers into links. If you press those links, a pop-up window will appear offering you the possibility to call the number after that or cancel. No need to take note of or even duplicate and paste the figures.