Phone # is invalid some places

Several years ago like late 2017 or early 2018 I got a new phone #.  They gave me a new area code for my city.  It’s a brand new area code.  And still some places when I try to sign up it says invalid phone #. Like right now I can’t get an account with the IRS.  How do we get this area code registered everywhere?   Oh, I’m in Sacramento, CA and they ran out of 916 phone #s and the new area code is 279.       

 No sub forum subject fits.  I have Apple iPhone SE