help! What is my right?

Our parking spot was ocupied by other person,but manager blamed me for calling him.
We live in an apartment and pay additional money for a guaranteed parking space. But this space was sometimes occupied by some strangers. We did not complain to manage before since it was in daytime and we found the persons and asked them move the car. But today, when we came back home 11:30pm, a strange car was in our space. We call the manager and he asked us to talk with a on-site person who taking care of the parking issue. Then he asked me to park behind the car, then he said I should call police. Anyway, finally he blamed me saying I lied to him and I should not call him. Another person working for him asked us calling police.
Does anybody know what should the manager do under such situation. I think the only thing I should do is telling him what happened and he should deal with it. I paid for parking, he should take the responsibility. His assistant refused calling police and he said our parking space is block, so I should be the person who call the police.
They did not do anything to that car. I was told such thing happened before and I guess it will happen again. What should I do? We (including my 5-year-old daughter) stood outside in chilly weather till 12:30 midnight. The manager treated me like a trouble-maker and was really unpolite to me. But we are the persons suffered and our space was occupied.

Any suggestions? Thank you very much!