It's not illegal or unusual for the affidavit to support the filing of a petition on a debt (or a suit on account) to be signed before the lawsuit is even filed.  Many firms will have all of the documentation lined up before they even file the suit so that they can quickly file a motion for summary judgement to dispose of the suit on the account.  The timing of the execution of the affidavit can affect the quality of the affidavit (for example, not reflecting current payments), but the timing is not a basis for its exclusion.  The main thing is that it is signed by a person with knowledge of the events outlined in the affidavit.  You bring up a secondary issue in your question--- which is not knowing about the lawsuit.  You need to find out how they perfected (or claimed to have perfected) service on you.  Service is the process by which you are supposed to receive  notice of any lawsuit.  If you didn't have notice and they didn't follow procedures, you may have a couple of defenses, but only if you act quickly, now that you know it does exist.