Updating my resolution for any who may search for number portability issues between carriers on the same phone with esim capability - same phone, keep number, but change carriers. (vs getting a new phone with same number, or existing phone with new number).
My iPhone 14 Pro Max was with Verizon and my long held phone number in the primary esim slot. I ordered service on Tmobile for my BYOD iPhone, iPad Pro, and Apple Watch 8. Tmobile set up my service on my iPhone 14 pro max with a temporary number that took the 2nd sim slot. iPad Pro data esim was assigned, and Apple Watch they are sending a physical sim to me, then I call back and they convert to a esim to enable the watch.
iPad Pro data came through no problem. Apple Watch process TBD, janky for sure to partition and ship a physical sim after the order, customer receives it, and calls Tmobile to set up the watch.
Esim didn't update my ported number - many phone reboots, emailed QR codes, Tmobile couldn't send anything to my phone since they showed the ported number active yet I was seeing the temp number I could call and text from but they couldn't. I couldn't create a Tmobile ID to get online support because it didn't recognize my ported number or temporary number. The temp number stopped working and so I had no way to call, text, or access support and verify my identity on my phone. Support model fail.
I went to a Tmobile store they saw my account from the ported number (YES!) where after a few tries of creating a new esim from their tablets and manually entering into my phone, they got the number in the phone and called to validate, and I used. It took about 25 minutes in the store.
Had I waited 24 or 48 hours as they recommend before escalating to their Transfer Dept, I'd have no working phone and everyone calling or texting my phone of 20+ years would get phone out of service or rejected text messages. And no way of accessing support without another phone to call from, and no way to validate who I am through their Tmobile ID. They will get my feedback.
In the future if I'm going to change service with the same phone (doubt I will) I would transfer my owned number to a Google Voice to hold it and have access to calls/messages, while getting a new account set up. Then I would port to a new phone when I get one or time port to existing phone allowing for no access for a day.
I see no apple or carrier information on portability and esim and this was my first one - and on the same phone. Who knows what the right process should be - and the carriers don't have anyone accountable to help you with barriers to complete the port, and you can't get into their system so it's mobile service purgatory. The company you left slammed the door behind you, and you're not really a customer of the one in front of you. If the magic doesn't work - bummer.
I'm going to take my concern up with both companies even if it falls on deaf corporate ears.