By now im sure you have got that plug out somehow..but anyway here are some tricks for loosening stuck fasteners i have used -
*tap the fastener with a hammer. Dont beat on it, just gently tap it. You should not be leaving any tool marks, just go tap tap tap for about 30 seconds. It doesnt hurt to douse the fastener with wd-40 or something close either.
And when this gets old, try loosening the faster now, it might come loose. If not - on to the next one!
*put a wrench on your hex wrench you are using on this drain plug. To give you more leverage - hold it close to the fastener hole for leverage.
*Heat - low flame from a propane torch (last resort). I mean LOW the lowest it will go. A heat gun might be safer and might help too. Apply heat to the fastener for 30 seconds or so, keep the flame moving. Shut off flame, try removing fastener.
*Use a breaker bar on your wrench, anything that will extend the handle; again, to get more leverage.
*Try TIGHTENING instead of loosening! For some bizarre reason this often works. Putthe wrench on, now tighten for a second or two Try to loosen again. Now tighten again. Loosen. You get the idea.
Any or all of these tips ought to help you get that plug out. And right about now i'd be vowing never to put my car again in the hands of the idiots from jiffy lube or whatever place tightened that plug so damn much!