> I am currently paying a ~$150 per month "tax" to AT&T to keep my US number while living abroad just so I can get login codes for websites that still have that number

Port it to a VoIP company like DIDww, spend $2.50/month, and received SMS can end up in your inbox if you wish.

If you ever want the number on a mobile account again, port it back out to your choice of carrier.