I pay by year, so I don’t know. I only use their lowest tier plan so it’s only like 12 bucks for the year. But I do think you have to manually do month by month. Sorry I can’t help. But the service has been very good. I just need a basic email account that’s private.

I use mailbox.org instead. Works well. Forget proton.

Running my workstation and server on Debian stable. Debian always. Debian forever.