It makes literally 0 sense to force 2FA upon people. Big annoying warning that says "2FA is very recommended" it's ok, but not forcing it, there is a reason no exchange does that. I use public numbers to bypass SMS verifications all the time myself because there's no reason you would need to give personal data at that level to do that. Again, there's a reason you don't need phone verification in any exchange to log in and do basic alt to alt trading. Of course, when fiat is involved, it's normal to start wanting more credentials, but forcing people with phone verification alienates people to use your service.

If you live in a third world country, or lets say you don't have a smartphone (a LOT of people still don't), you can't use Google Auth which leads to being forced to check your phone every single time you log in. This is a big no-no.

Reconsider how you run this.