@Korth wrote: Maybe change your phone number, lol.
I think I should expand on what I meant by this.
You could of course change your Public Mobile phone number any time through your Self-Serve. No cost (free). No hassle (aside from perhaps a few hours or a day of interrupted phone service, along with a restart).
But of course you'd then have to inform all your contacts of your new phone number, which is a hassle. And your old phone number would likely be lost forever.
But there's an alternative. You only need this phone number for what amounts to being a one-time 2FA. So use somebody else's phone and phone number (with their permission!) for this purpose - spouse, friend, family, whatever. Once you've passed Steam's account authentication you can login to the account and change details (like phone number) as needed.
No need to try taking down the castle walls when you can just enter a side door.
Thank you for getting back to me.
Updates on removing the number from our inventory should take effect within 24-48 hours.
If you are still having trouble with after that period, please see https://freecarrierlookup.com/ > enter the number and confirm the carrier listed. You may then need to contact the listed carrier for more information as we would have then completely cleared the number and have no further ties/control.
Best Regards,
XXXXXX
Line2 Support