Tried it today after I ran out of my patience level for T-Mobile to pick up Postpaid e-SIM support.
Edit: Both were phone calls
I repeated per instruction, "I need your help with a SIM swap, here is my EID". The first operator asked what was it for, then I told her that I'd be traveling internationally and that I'd have to free up my physical SIM slot. She asked me if it was for e-SIM and I had to say 'Yes'. After being placed on holds on & off for 1 hour, their so-called "technical expert" came back and said, "Sorry, e-SIM support currently is only for prepaid".
I tried the next time. This time, all I did was the following to get the job done:
Me: I need your help in a SIM Swap, here is my EID
Rep: what is it for, an e-SIM?
Me: yes
Rep: Let me check.. hang on for a minute
Me: waiting
Rep: Sorry, we don't support e-SIM for Postpaid yet
Me: Alright, let's forget about this whole e-SIM thing. All I need your help now is doing the SIM swap, please. I completely understand if anything goes wrong, that it would be my responsibility.
Rep: Sure, what is your EID?
Me: Blah blah blah, Meh Meh Meh
Rep: Here is the confirmation PIN. Read it back to me
Me: Baa-baa black sheep, have you any wool...
Rep: Turn off your device and let me know what you see (I had initially called her on a different phone number, not on the one I'm activating the e-SIM)
Me: it says, No-sim and no coverage
Rep: Sorry.. Like I said, Postpaid e-SIM doesn't work
Me: Can you help me get the activation code via a text, please?
Rep: Sure
Me: Inputed the SM-DP + Address manually and the activation code from the text
Me: I've T-Mobile Signal now, thanks!
Rep: You're so smart! How did you do that?
Me: Duh!
Lol, JK... thanks a lot to everyone involved with this thread.