Number Transfer Pin for a Landline

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The topic to which spoom2 refers dates from March 2022. In it, MC94115 says:

For anyone reading this in March 2022...

For old ATT landlines, traditionally ATT landline customer agents would ask for the 3 digits following your phone number at the top right of your landline bill to confirm your identity.

It would read "XXX XXX XXX YYY Z". 

XXX-XXX-XXX would be your phone number with area code.

So they would traditionally ask for what YYY was. 

Your landline "account number" is basically the whole thing XXX-XXX-XXX-YYY-Z

The PIN number (used for PORT requests) is basically YYY-Z (four digits).

How they came up with the PIN number was basically taking the 11th, 12th, and 13 number of your account number "YYY" + the last digit (aka 14th digit) of the account number "Z" to give you the PIN which is YYY-Z (four digits) 

Put another way, the last four digits of your "Account Number: XXXXXXXXXXYYYZ" is your PORT PIN: YYYZ

As far as I know there was no way to change this PORT PIN, manually or with online access because this was simply an account number assigned by legacy AT&T. Some of the responses above referred to a PIN process with ATT Mobile but were not applicable to ATT landline.

Hope this helps, cheers. 

I have no idea if this is still current. I need to port out an old landline myself.