It appears that maintaining a contract cell phone
in your name is no longer
the only way to get access to IRS "Get Transcript" and related services protected by the fairly new IRS Secure Access Authentication platform.
This was personally causing me some trouble in that I only use pre-paid / pay-as-you-go types of cell phones. I would have been happy to visit an IRS office to authenticate myself but that has not been an option.
There now appears to be a US Mail based authentication method, in lieu of the contract cell phone, that is available to initially setup your account.
A cell phone is still required to receive the SMS two-factor authentication codes each time you access the system going forward.
From the IRS page:
Note: If you have a pay-as-you-go mobile phone or a business/family plan mobile phone not associated with your name, you may request that we mail an activation code to the address we have on file for you. You still must have a text-enabled, U.S.-based phone to receive a security code text that completes the validation process and allows returning users to access their accounts.
Additional details can be found at the IRS page
for the Secure Access system.