How to make phone number a Click to Call on Phone?
After making various finding we come to conclusion to have following
Wrap all phone numbers in hyperlinks with the tel: schema.
Always use the international dialing format.
NIST Telephone Time-of-Day Service <a href="tel: 1-303-499-7111"> 1 (303) 499-7111</a>
This we found on google developer page and found it working
If you want to detect phone browser etc following articles will be useful