Answered by Stephanie, Hiring Expert at AT&T Inc., on Monday, June 25, 2018
Well now, that's just a question for Emily Post (manners maven, look it up if you're interested in all things etiquette). During the hiring process, it is appropriate to use Mr./Ms. when speaking to someone more senior. The time tested phrase of...Mr. So and so, may I call you John? It's polite, its to the point, and it makes the situation clear as day.
It may seem a little formal in our increasingly informal business culture, but it also demonstrates respect and could set you apart from other candidates.
After you're hired, you'll get a solid feel for the style of the organization. But if you can't wait and you want more culture based info, do some networking with current or former employees to get the skinny on expected formalities.
Best of luck!