multi factor – Anonymous SMS-based auth: How to get phone numbers to receive a single 2FA authentication SMS with minimal cost and effort, multiple times

What is the simplest, fastest, cheapest, easiest way to get access to a ‘non-VOIP’ phone number just long enough to receive a single text message?

Traditional approaches that are not ideal:

  1. Use existing mobile phone number. Compromises anonymity.
  2. Go to the store, buy a burner SIM, buy some minutes, set it up. Probably the best approach, but relatively costly and time-consuming… to receive a single text message! Cheapest I’ve seen is about $10USD for the SIM, plus about >$10-20USD for some ‘days’. Also, considerable hassle to set this up, from going to the store to calling the carrier to scratching off blah blah blah.
  3. Use one of the many burner SMS services, eg, many others, or use Twilio, Google Voice, Skype, or other online-services. This doesn’t work on the site. Need a ‘non-VOIP’ number, presumably registered with a standard carrier, see below.
  4. Ask someone else to receive the text. Creepy, and, well just not good.

Why / use case
In order to create more than one account on a website that requires SMS-based 2FA as a test to prove that you’re human and allow registration for the site. The site doesn’t store the phone number for later 2FA as would be typical for password retrieval, so the number isn’t needed again later. It is only ever needed to receive a single SMS. Caveats regarding the number:

  1. It has to be a phone number that has never been used on the site before.
  2. It cannot be a phone number that the site deems ‘VOIP-based’, see above, or it won’t work.
  3. Want at least reasonably decent anonymity, so not trivial to connect the phone number to the registrant, as it would be for a personal mobile number in routine use.

Want to do this multiple times, so want an approach that is inexpensive and non-time-consuming. Does not matter which country the phone number is associated with it appears.