When a website visitor on a mobile device like a smartphone uses a click-to-call button or link on a website, a dialog box with options to Cancel or Call will appear.
In some cases, due to an update to the Safari browser for iOS, an error message may display that reads "This website has been blocked from automatically starting a call". This message occurs after a user has clicked, then cancelled a call three times.
If this message displays, it is not in error, it's simply a tool used by Safari to try and stop automated call links from sending spam. To place your call, just click Allow Call and the phone call will be placed successfully.