The Wall Street Journal has electronic cancel. I did so temporarily. At first I was super impressed. Then I remembered that it was really hard the first time I tried years ago.

Turns out that California SB 313 changed the game https://leginfo.legislature.ca.gov/faces/billTextClient.xhtm...

Online registration means you need online cancellation.

Actually, reading the bill, only the intro seems to imply that. The text doesn't. Either way, a pre-written email should suffice.