FINALLY. I've got to share this so you will have a smoother journey.
The task was to set up a phone at my girl friend's house. She wanted the number to be the one from her recently deceased parent's home.
Her parent's account was closed last May.
AT&T opened an account, using the number, in my name and her parent's address. Google Voice will not accept old land line numbers, only active mobile accounts.
At T-Mobile, an account was set up to port the number to a SIM card. A temp number was assigned the SIM card. T-mobile does a credit check, but I had frozen my credit reports after the Equifax data hack last year. I had to unfreeze all three major credit reports before T-Mobile would continue. AT&T ported the special number to T-Mobile SIM. Cost $26.81.
Google Voice requires an Active Mobile phone with the number being ported.
I had to put the T-Mobile SIM in a mobile phone. I happened to have an ancient Sony Ericsson Walkman W518a, but it was locked to AT&T. Back to AT&T to un-lock the ancient flip phone using a request form on their website. Filled out the unlocking form with a long number from inside the phone. Submitting the AT&T form returned a request number. The next day, AT&T sent a message approving the unlocking, providing an unlocking key (another long number) and unlocking instructions. Entered the numbers; a couple of tries needed. I put the T-Mobile SIM card in the flip phone and after a few gyrations, the flip phone would answer to the special number.
Back in Google Voice, System; Phone; Legacy; was able to request that the special number be exchanged for the Google Voice generated number. Paid $20. You can check the number portage progress through your Google Voice account. After a couple of days of anxious anticipation, Google Voice accepted the special number for it's account. Then applied for the Anveo E911 service on line SP2; $25 on PayPal only.
The Google Voice portage acceptance from the T-Mobile SIM should have automatically closed the T-mobile account.