Changes to Database, but Web Interface overwrittes it

I’ve created a custom extension to change the conference (Meetme) password.
It’s very simple, it creates a random password and updates it to the ASTERISK.meetme, column userpin.
But the as soon as I access the Web Interface, it deletes the password from the column.

Where else should a change it?

All interaction with FreePBX should be done through native methods and functions. You should never manipulate databases or files independently.