As one who's been in this situation **many times,** there's no good answer outside of quitting. Which doesn't appear to be an option. :-) I call these "corporate shenanigans" even if it's a small company. A few items to look at:
Policy: Do you have an "official" job description, as in, on paper, something quantifiable? It doesn't sound like you do, but if you do, this is really your only leverage.
Pliability: "He who has the gold makes the rules." Not really true, but in the context of an employer, this is how they see it. What is your relationship with the employer, can they listen to reason, or is it "put up or shut up?" If they are inflexible, by bringing it up repeatedly or bucking their wishes you're going to be seen as a troublemaker, and they will figure out a way to let you go. And hire someone for less money to replace you. You're expendable, this is how it's seen, so tread carefully.
Job value: So you're doing tasks you feel you should be paid more for, and are probably right. But you have a job, in a time when many people are living on the streets, you have insurance, and even though you're not appreciated, like it or not, every thing you do in web development expands your experience.
Sometimes it's mind numbing, but every time you adjust another script, it's likely you'll learn something new, or at the very least, get better and faster at what you do. In this respect, you have access to a venue of experience that others don't, even if it feels like hell. So are you seeing this aspect of it, or is it all about "more money?"
Add these three up, I've been in these situations and when the employer won't move, your hands are tied, you really have two choices. See the best in it or heave ho matie.
A small anecdote, and listen carefully to this one:
but they are only paying me to to tech support
I was "Senior Web Developer" (tongue in cheek, this company offered titles, not raises)
at a Northwest ISP with the same sort of corporate shenanigans going on. In the next room was tech support, and one day they hired this guy at minimum wage. I got to know him, and the guy is a freakin' genius. Almost every day he helped me solve things I couldn't, and I always asked what the heck he was doing here. He was biding his time, gathering his forces. One day he'd saved enough from his minimum wage to float for a couple months, and quit.
He had built this web site that was gaining momentum, based on a very simple concept, something that a lot of people need. Two years later . . . the man is a millionaire (and my hero.) :-)
So advice? It's up to you, but it's all in your hands. This job is temporary, like most things. Focus on what you want out of life, and keep the job until you find it.