Basically yes, IT dept or IT personnel on non-IT company are just supporting roles. How should I put this? Supporting roles are important too. Without you, they'd die as well.

Its like how you play an online game. Example: Ragnarok Online. Do you think a Knight can tank Osiris without his Priest friend? Impossible, right? Well, just look at it that way and you can see the pict.

same here also, i feel jz like a fool and sad in my company cz :

1. my basis RM 1350, my job function as technician, but beside IT technical support, i have to handle:
a. server administration and security system
b. mail server, user email transaction monitoring
c. give IT training for boss / end user
d. IT hardware and software asset audit
e. company website design and website visit counter monitoring
f. networking
g. 5 companies IT facilities monitoring (1 headquarter, 4 subsidiaries), but my salary paid by headquarter only.
h. security system, CCTV, door access, guard alarm
i. telephone system
j. call cost saving monitoring, bill statement checking
k. color printing, scanning.
l. maintenance job like wiring/cabling, repair photostat machine, repair air cond, repair telephone, repair printer, repair flouresent light
...... and many more, can say that my job function is BSBH.

2. some stupid end user
a. who always show off, act as know all of IT knowledge, so they no need IT people help.
b. who keep on challenging my skills and post since they assume they know very  well in IT field.
c. when thing goes wrong, some stupid end user also denied that they never did anything wrong.

3. my stupid boss who doesn't understand IT:
a. assume IT as nothing but wasting resources and money.
b. doesn't approve my request to hire 1 more assistant since i'm the only one handle in IT DEPT and have to handle 5 companies IT facilities.
c. always ask repeated question althought i answered it before, somehow they also ask a lot of nonsence question and task.
d. always give insufficient time for any difficult task, they think IT people is easily handle.
e. when they need help or you help them settle their IT problem, they will praised you, once they no need any help, they see you jz like s***.

really feel upset...........

Then wat r u waiting for ?
Go some where who really know how to appreciate you.

If you still wanna stay, there is a solution for you.

On leave for at least 1 - 2 weeks . During your day off don't receive any call or access email.

Just wanna show that how important you are, see who else going to support thier IT fac within this period. 

they will not value this way...oni when they need da things, they wil jump on you. they wont see da big picture...they rather waste 500k for a BMW than invest in a backup server rm30k as they cant see it in front of their eyes

Then wat r u waiting for ?
Go some where who really know how to appreciate you.

If you still wanna stay, there is a solution for you.

On leave for at least 1 - 2 weeks . During your day off don't receive any call or access email.

Just wanna show that how important you are, see who else going to support thier IT fac within this period. 

That is very true....let them know....besides i think ur salary is too low, with ur capability i think u can get at least 2k outside, don be regret to leave

These several points very true indeed.
Especially the bolded one, sometimes they didn't even say thank you and give you those "long long" face like you have been causing all those trouble to them.