I transfered my number from at&t to Visble today. No idea if this helps or not and just want to share my experience to you.We used billing PIN as port out PIN before at at&t but from 10/18/2021, you need to request port out pin at at&t side and the number expires in 4 days. The port out PIN should be 6 digits instead of 4. Here the link how to request the PIN https://www.att.com/support/article/wireless/KM1447526/
Hope it helps you.
Thank you. The port out pin from Verizon was the only bump in the road I had when moving to Visible 2 days ago.
I thought it was the 4 digit account pin and attempted too many times locking the transfer for 24 hours. That gave me the time to find the proper way to get a Verizon port out 6 digit pin. Here are the Verizon steps