Call more than one person and keep a list of your calls. If you report a flagrant violation and staff response is slow, call the press, especially local papers such as the extras and neighborhood papers, and your local TV station. Of course it's best to get involved before trees are cut down. Your neighborhood association should keep informed especially of zoning changes and applications for development in your area. Watch for postings for new zonings, variances or tree removals, however these may not accurately indicate the true status of a project.
Appeals can save trees and improve landscaping plans if done early enough.
When trees have been cut down, it may be in violation of a tree protection ordinance. Other ordinances have no protections at all for existing trees of any size. It is important to know what's legal and what's not according to the tree ordinance for your area. Homeowners have an exemption and may cut down five trees, as long as they are not large specimen trees, per year on their property. In the City of Atlanta, there is no requirement to save existing trees per se, but developers or homeowners must receive a permit to remove any tree over six inches in diameter.