i don't think you are overpaid, sounds like you are glorifying your job though.
I do AD stuff.. I put some people in the right group. Does that mean i know AD? No.
Answering a few calls and doing basic things in a few areas doesn't deserve much pay.
Tend to agree, it's a first line role so would expect a salary range of 15k-20k which you are in.
Use it to gain as much knowledge as you can, support jobs like this are a great start as you get exposure to loads of stuff, just not in much detail (jack of all trades, master of none).
My first job was part of a desktop support team but we did 1st and 2nd line, project work (I spent the last 2 years there purely on projects), enhancements, looking after some of 'our' servers, the telephones etc.
Starting was about 16k but moved up over time to 27k before leaving, that was over about 4.5 years.
I've been gone from there 2 years now but my other half now works there effectively doing my old job and their starting range was at the top of my range and they are now 1st line only (they split the one big team up we had into 3 or 4 smaller ones).
Big time underpaid if you are doing all that on that low wage, ask for a pay rise or leave, if you are that valuable to the company they will beg you to stay and give you a whopper of a rise, otherwise get down the Job Centre you dole scum.
Doing all that? Not belittling the job at all, but as Morba says it's basic admin stuff really, designing the AD, setting up the servers, installing the BES etc would all be deserving of the higher wage, but just admin not imho. Although I'd say 18k would be reasonable for that.
And as for the leaving thing, most decent companies wouldn't bat an eyelid if someone left. Yes they might be sad to see you go, but no one is indispensible! When I left my first job I had a nice chat with the big boss, she asked what they were offering and they just couldn't match it no matter how much they wanted me to stay.
At the end of the day if that's the stuff your team does get as much out of it as you can as quickly as possible and move on either internally to another team (server team, networks team etc) or to another company.
Although totally contradictary to all that our trainee desktop support guys start on almost 22k moving up to 30k over 3 years and they have an easy easy life!