Law Firm Keeps Using Old Mailing Address

Can anyone give advice on how to get a law firm to send documents regarding my lease and drilling to the correct address? I have called them twice, and each time they tell me they have corrected my mailing address, and yet today the mailman from the town where I lived many years ago called to ask my address (once again) so he could forward the email. If I weren’t for the mailman who knows me personally, I would be missing out on a lot of important mail. Any advice?