Look in your browser options and see if there is a Skype Click to call add-on installed. If so just disable it. What it does is to highlight any phone numbers on a web page with a button which allows you to click it and it will be called through the Skype system. I found it pretty useless so I just disabled the add-on and no more problem.
iPhone 7 review: a range of small updates add up to an excellent phone