How to Make A Specific Website URL AutoDial A Phone Number?

As maybe some of you know, almost half of traffic from YouTube is on Mobile and currently YouTube doesn't support External annotations from mobile except for Call-to-Action overlays.

I am trying to set up a "Click to Call" overlay for Mobile user, so when they click this Call-to-Action it will go to a specific URL on my website (ex. abc.com/clicktocall) and have it auto dial/call a specified phone number.

Is it possible to set this up using a script without them having to click another link once they land on this page or does anyone have a different solution?

Thanks!