The number, everywhere it's needed
Top of the page, in the opening section, after every answer, at the bottom. Tap to call on a phone. A callback request for people who can't talk right now.
Tell people what to say
Name, callback number, address, city and ZIP. Which fixtures are affected, when it started, and any previous work. Customers feel prepared, and the office gets what it needs on the first call.
Make a promise you can keep
Mike or Tom calls back within one business hour, 8 AM to 6 PM Central, Monday through Saturday. A promise with hours on it is believable. "We're always available" is not.
No fake urgency
No countdown timers. No "only two spots left." "No charge to request the call" is the line, and it is true.