I would need more information to properly answer your question. There are certainly laws that deal with your right to be free from random entering your apartment. Also, however, you need to look at what your lease says when they can enter. What kind of entry is the apartment complex making? What are they doing while there? Why are they saying they are entering your apartment?
Nothing in this communication should be considered legal advice. Nor should this communication lead you to believe that an attorney-client relationship has been created. Only after thorough analysis of your case with you in my office can I provide effective legal advice on your specific issue.