Apartment complex won’t give us access to the mailbox

[US-Florida]

As stated in post above my apartment complex is bs’ing about the mail key. I’ve been living here for 2 months now almost 3 and they keep making excuses “how they’re working on it”. I’ve called the post office and filed a report already 3 times. The post office says the apartment complex wants us to pay for the locks to be changed but this wasn’t in our rental agreement or anywhere on paper. When I talk to the apartment complex they make excuses and say they’re working on it again but never they want us to pay. I’ve flat out refused to pay straight to their face already and they simply aren’t working on a solution. I’ve also talked with the post man and he will open it for us if we ask him but he comes at weird times when we aren’t home or at work. I have a paycheck in the mail coming soon and it’s over $500. I’m not sure what my legal rights are especially if I can’t get access to my mail with money in it. I feel like this is thief and they are purposely withholding my mail because they are lazy.