Mr. Ennis:
"Charlie" (with "ie" not "ey") is acceptable, but "Semper" is okay as well, or "S.V.", even. "Charles" is okay, too.
"Mr. McCullough" is also quite acceptable if'n ya wanna be "formal".
But, if you really want to get my attention, try: "Did you drop this 100 dollar bill?"
For years, as a kid, I didn't fully understand first, middle and last names and nicknames and alternate names and pet names and such. I was called "Charles" by my teachers, "Charlie" by my Mom and Sister, "Chas" by a neighbor, "C.T." by my Brother and "Little Feller" by my Dad. But I also thought I had an extra last name of "Yougetinhere"... as in my Mother yelling, "Charles Thomas McCullough you get in here!"
Where I worked for 40 years we had to wear government mandated photo badges. One year the government required everybody to get a new one and somebody (don't know who) decided the badge was to show a "friendly" name in big bold typeface and the last name below that in smaller typeface. They erroneously thought that it would be better that way. I wanted my badge to read "Mr. McCullough" so that if somebody I didn't recognise approached me and they didn't know me, they would not be able to bluff their way into asking questions by calling me by my common "friendly" name. If all they could read was, "Mr. McCullough" I'd know they didn't know me. I got "overruled" and I accepted "Charles" (instead of "Charlie" which all my co-workers called me). IT WORKED! I caught a salesman trying to bluff his way into asking questions about a project by pretending to know me by calling me "Charles"...
"Hey, Charles, long time no see! Hey, what are we gonna do about the computers on this project?"
he he he he... I LIED to the fellow about lots of stuff and then reported him to management! Never saw him again.