NOTE: Click to call is no longer working in phones using Chrome. Alternate browsers like FireFox do work. I have posted a question about this in the Chrome Community and I submitted a bug report. FIXED: Chrome (mobile) has been updated to 76.0.3809.132 and click-to-call links now work correctly.
Put the following in the EMBED CODE option of the INSERT edit function.
<a href="tel:+1-303-499-7111">Click to Call NIST Time Service!</a>
<a href="sms://+14035550185">Send an SMS</a>
You can also use SKYPE by entering:
<a href="skype:echo123?call">Call the Skype Echo / Sound Test Service</a>
<a href="skype:SKYPE USER NAME?call">Call me on Skype</a>
The visitor must have the Skype app installed for the Skype link to work.
For the button I used this code:
View this page with your cellphone to see if it works.
<a href="sms:+1-4035550185"><embed src="https://dabuttonfactory.com/button.png?t=Send+Text+Message&f=Calibri-Bold&ts=24&tc=fff&tshs=1&tshc=000&hp=20&vp=8&c=5&bgt=gradient&bgc=3d85c6&ebgc=073763 "title="403-555-0185"</a>
The number in this example is a fake number that doesn't go anywhere.
You can also use Google Hangouts. Insert the URL 'hangouts.google.com'. You will be able to select to make a phone call or send a text or make a video call.
You can create a QR Code image for dialing. There are several QR Code generators, including an add-on for Chrome.