Withholding rent may lead to an eviction. Be careful!
This question is hard to answer without knowing your tennant laws for your city/state.
REALITY:
I suggest you actually speak to the property manager in person. This means you will need to visit the property office and speak to someone face to face. I found that letters and phone messages dont do much but a upset tenant in the main office is always taken care of quickly.
LEGALLY:
There are provisions that allow you to withhold rent but it doesnt mean you get to pocket the money. If you withhold rent there is a process you must follow that officially notified the property manager or owner. If you do not receive response or if the problem has not been resolved in a timely manner you are allowed to take your rent and use it to stay at a hotel. (This may end up costing you more in the long run considering hotels arent cheap compared to rent.)
Please check with your states Secretary Of State webpage to learn more about your rights as a tenant. You have better tenant laws if you live in CA, IL, or NY.
Considering the information you provided I do not believe you have much to work with. I had the same problem and the only viable solution was to move to another unit once my lease was up. I left once my lease was up, ended up buying my first home and became a real estate investor with the help of a local group.
Sorry for the bad news but that's the reality of living in apartments.
Good L.U.C.K. (Learning Under Correct Knowledge)