Ever since I started offering a 5% discount for Automatic Payments, I haven't had a problem.
I've only got one player who still insists on paying cash, and he's occasionally late, but he gets us discounts on our gaming books, so I don't mind giving him an extra week before enforcing the "No pay, no play" rule.
We always use DM. Even in the occasional D20 Modern one-shot. We just use it so often that nobody seems to mind, even if we use it when we're playing a non-D&D game.
DM is an old habit-type word. Always DM for D&D. For another system, GM could work, but I always remember DM, or we just ask "who is going to run the game tonight?"
Because the DM term is the property of TSR/WotC, we have gone by the GM term for a long time... Although some games tried to shoehorn us as Referees, Administrators, Keepers, StoryTellers, Judges, Arbitrators or even the "Corporation".
The side effect of being the GM is that some players (many players) mispronounce it.
You see, I am the Gay Master. I have complete mastery of the Gay Mechanics. They dance for me in their leather chaps to the Village People.
I actually try to charge people $5 more if they don't call me the appropriate honorific: DM for D&D, GM for everything else. Hyp, I'm going to have to go to automatic payments as well; without credit card numbers on file, the fine is hard to enforce.