You can call the CWP using Open URL. How did you use the url?
If this works on clicking link, you can automate it.
Set Web viewer [ "data:text/html,<a href='tel:1-800-123-4567'>click me</a>" ]
I have tried that. It does not work in Web Direct on an iPhone.
Sorry I don't have phone.
If anchor don't work, how do you call the URL in your CWP?