Sometimes that is all it takes—something simple like a letter or just to have an attorney show up—to stop the necessity for further action. If you start with the simple attempts you may be able to avoid the more complicated (and expensive) tries.
In some legal problems, the earlier you address the matter properly, the more choices you have available to you. Often the longer you wait, the larger the problem becomes, the fewer options you have to resolve it, and the more it is going to cost you. If you seek legal counsel early on, you may be able to aim towards a better case scenario (rather than the most expensive outcome).
A letter is a lot cheaper than a lawsuit. You may want to talk to an attorney to try to “stamp out” a problem before it becomes part of a legal procedure.