After buying our house, we kept getting important official mail from some governemental org, concerning not the previous owner, but some completely different g

After buying our house, we kept getting important official mail from some governemental org, concerning not the previous owner, but some completely different guy, we dont even know who. We always sent it back noting wrong address, and they kept sending it right back to us. We started to get 4 or 5 of these letters each week. One day I got sick of it and wrote 'Has been swallowed alive by crocodile' on one of these. Someone took notice, presumably, as the mail stopped.