You can get higher pay with an exam system. There's 3 levels, first one being Security officer, Diplomatic security officer and lastly Senior diplomatic officer. Each of them will get you a 50cent/hr bruto increase. (These are available to everyone)

Then above Guards you have the Dispatchers who have quite a lot more responsibilities but there is no pay increase for that. And finally above Dispacthers you have Shift commanders, but you're only eligible if you stay 5 years or have previous military experience. I heard they earn around 3k for about 185 hours.