Problem with adding a phone number to an account Battle.net

[Nicole-1893]

The developers covered their stance on phone numbers you can use here:

Defense Matrix – SMS Protect Update with Prepaid Phones

Since introducing Defense Matrix, our new initiative to stop disruptive players in Overwatch 2, we’ve successfully taken action on thousands of accounts that we’ve found to violate the Blizzard In-Game Code of Conduct. We have continued to listen to player feedback and evaluate our barriers of entry that can prevent players from being able to join. As a result, we’re making a new change to our SMS Protect Requirements to play Overwatch 2 starting with today’s patch. Effective immediately, anyon…

If your carrier is classifying your number in another way, you’d need to take it up with that company.