The question is specifically related to On-waves, a Cruise Ship cell network that connects when you're out of port (or more accurately, outside normal cell service range). The service isn't included in the T-Mobile Simple Choice plan and is ghastly expensive. I accidentally left it on once, and burned through like $500 in data charges before I got the T-mob warning. They forgave it once, but I've burnt that bridge.

So the question is, I just want to disable my phone from ever connecting to the On-waves carrier, and I can't find a way to disallow a specific carrier forever. I can choose a carrier by turning off automatic, but that's the opposite of what I want, I want the phone to never, ever connect to this specific carrier. I also don't want to disable data since I'd rather the phone connected to every available carrier other than On-waves, since that is typically the only one not covered by Simple Choice where I travel. And, of course I'm now paranoid about forgetting to turn it off again, going to dinner and coming back to find that the ship has cruised out of land service range and I've just spent hundreds of dollars.

Am I missing something obvious?