List of 5G phone offers per the network-wide update from 3G in 2022?

My experience so far. I was surprised to receive the text message below. I initially assumed it was spam but the last four of my  number and partial IMEI matched my flip phone on a legacy prepaid account I've had for a very long time ( like to have a backup phone on a different network ). I still felt the offer would be invalid for my phone and service type. 

Having a little extra time,  I drove to T-Mobile and went for the"free" (about $60 with fees) phone. She was very nice looked at the text and got a new phone out. All was going fine until she tried to cash out and did not have a valid mangers promo code. She also mentioned it would free after monthly credits on my bill. I have prepaid account so things are not looking good.

At this point she remember another employee/manager worked  on the same offer . The employee was called and asked how they completed the transaction only to fine that it had not yet been resolved. She took my contact info and said she will get back to me with a answer. 

I suspect a prepaid account let alone  legacy prepaid account will not result in "free" phone without an account change. May have to drop second line or port out. Will see what happens.

T-Mobile: Our old network is retiring! Trade in your phone for a FREE OnePlus Nord N200 5G by July 1 to prevent service interruptions. Don't wait - upgrade your device associated with the line ending in #### (IMEI containing ######). Learn more: t-mo.co/Free5G