Unblock Amazon Prime SMS # to receive security confirmation

I have Xfinity and apparently have blocked Amazon's SMS number so that I am unable to receive a security confirmation on my iPhone to access my account on my laptop. I called Amazon and they said I need to talk to Xfinity. I called Xfinity and they just told me how to unblock numbers (which I know how to do). I have lots of blocked numbers and don't know which one is Amazon's.

The last thread on this topic is from 2018. Does anyone have any current information? Thanks!