If dialplan matches, play announcement instead?

I converted one office from an old system that required users to dial 8 before getting an outside line. On their new freepbx I have a dial plan that will accept calls with a preceding 8 or direct dial. Now that some time has passed, I’d like to see if users dial a 8 before their number an announcement could be played back “it is not necessary to dial 8 before calling this number”

ie, if the user dials 8XXXXXXX or 81XXXXXXXXXX play the announcement. Is this possible?

You can do that in your /etc/asterisk/extensions_custom.conf

creating a context called

[macro-dialout-trunk-predial-hook]

This ref gives the howtos quite clearly, just modify to suit