Creating the correct format for your telephone number links is important because different devices react differently. I prefer to use the folowing format.
Tel: <a href="tel:+18057460079">805-746-0079</a>
<a href="facetime://8057460079">Facetime Us</a>
I add the Facetime link, not because I want to be contacted via Facetime but, because clicking the default tel format on a Mac causes the Mac to try Facetime but the number format is not correct. The links above look like the following:
Tel: 805-746-0079 Facetime Us