Unlocked Device Problem with Xfinity and Apple

I bought an iPhone12 which is supposed to be unlocked by Xfinity. I have an email from Xfinity that confirms the device is unlocked (The original owner forwarded this email to me). However, when I erase and restore (multiple times), the Carrier Lock on the device keeps showing "SIM locked". I also tried to activate it with TMobile & SimpleMobile simcards, they both do not work. It is very frustrating that the original owner already contacted Xfinity for me a few times, and they said the device should be unlocked. How do I get it change to "No SIM restrictions"?

My question is if this unlocking problem was because Apple has not yet complete the unlock request from Xfinity for my device? What should I do to get it unlocked? Can Apple help me to resolve this issue?