I have the same problem in my apartment complex with my reserved spot.

You might see if there are signs on the property that state "you will be towed" etc. We have them posted all over our apartment complex at every entrance and it states that parking in a reserved spot will result in an immediate tow.

Our apartment complex has a deal with a local tow company (they "cover" our apartments). So you might see if the office has the tow number or if there is a tow number on the reserved parking signs. After it happened to me once, I put the number in my phone as "Tow Guy". All I did was show the guy my parking tag and he towed the offender. Sweet justice!