Nuked plans: Oops! There was a problem with the SIM transfer request from your Apple Device.

Source: iPhone 7 with physical SIM

Target: iPhone SE (2020) with no SIM

Goal: transfer ATT cellular plan from iPhone 7 to iPhone SE (2020)

I followed the advice: Transfer or convert your current SIM to an eSIM on your new iPhone - Apple Support

At the last stage, while converting to eSIM, I get:

Result:

Oops!

There was a problem with the SIM transfer request

from your Apple Device.

We can help, please call AT&T Customer Care: 800-

331-0500 (or 611 from your mobile device)

Note: Now I can't call from the iPhone 7 or the iPhone SE (2020). I can't call 611 or 800-331-0500

Is this normal? Should Apple put a warning: In case of errors, both phones may lose cellular connectivity?

BTW: Choose a different device doesn't let you choose iPhone SE (2020) or its equivalent while submitting this ticket.