When you're being sued on a debt by a debt collector, one of the best things you can do is often to file a counterclaim. This might be based on any number of laws, but most typically you will have a claim under the Fair Debt Collection Practices Act. Particularly if you are pro se (representing yourself) you should probably expect the debt collector to file a "Motion to Dismiss."
Legally, a motion to dismiss is designed to "test the legal sufficiency of the claims." That is legalese for deciding whether the law makes what you claim happened illegal, gives you the right to sue the other person, makes the other person the right person to sue, and so on. In other words, if what you say is true, does the party you are suing owe you money? Pragmatically, the motions might be more a way to force you to restate your pleadings to be more specific, to test your willingness to fight the debt collector, to please a client, or just an easy way for the law firm either to train new lawyers or generate fees. You will probably never know the actual reason for the motion, but if it is granted, your claim will be dismissed (kicked out), so you must take it seriously.
On a motion to dismiss, the court is required to consider every fact pleaded in your counterclaim (I'm assuming here that the debt collector is bringing the motion against your counterclaim) as true. Given the truth of what you say, the debt collector will argue that the law simply does not provide you a remedy. Actually it goes further, though. The question before the court is whether there is any set of facts, consistent with your pleadings, that would give you a right to sue.
If you are opposing a motion to dismiss, your general strategy should first be to relate your claims to the words of the law under which you are bringing your claim. If the Fair Debt Collection Practices Act says (as it does) that the debt collector must stop calling you at work under certain circumstances, for example, and your claim alleges those circumstances and the fact that the debt collector continued to call, then you will defeat the motion.
Sometimes it is not so clear, obviously. Debt collectors are prohibited from various "unfair" or "deceptive" collection practices, and not all of these are specifically enumerated in the law. In that case you will want to find a case involving similar actions where courts have declared the practice illegal. Failing that, you will make the strongest logical argument possible that the action in dispute is unfair or deceptive.
Remember that although every fact will be considered in your favor (every "close" question of fact should go your way), the court will decide close questions of law. That means that even if the judge thinks that calling you seven times in an hour is unreasonable and illegal, he might decide that calling you six times was not unreasonable. That is because the question is not how often you were called, but whether the number of times called was "reasonable," a decision the judge is supposed to make. For this reason, it makes sense to state the facts strongly and make your best case.
