If I were you, I'd go back in there and pronounce each letter individually, in order to avoid confusion. I'd bet 99.9% of the world phonetically pronounce it, as it has the word mole in it, with an x added at the end. Mole. X.
But really, take my advice on individual letter pronunciation.
Emm. Ohh. Ell. Eee. Ecks. Then reach over the counter, grab him by his clip-on tie, with your other hand, rip his pocket protector out and hold it over your head. Pull his face REEEEEEEAAAAAAAALLLLLLY close to yours, so that, in your rage, flecks of spittle will cloud his vision through his glasses, and whisper Clint Eastwood-like to him "listen Poindexter, if you wanna see this pocket protecter and all your "good pens" in there ever again, you'll listen to how I say it, you'll say it like I do, and you'll like it. If you've got any questions, I'll gladly get you a Shutup-sicle
TM for that gaping maw on the front of your face".

Or you could just ignore his mispronunciation and go about your life

(I came up with that after seeing pointdablame's avatar - can you picture going into Radio Shack and unleashing hell on 'em?
