transferring Att number from Wireless Internet (IFWA40) to motorola unlocked phone

We have an ATT number we use for the house through a Wireless Internet (IFWA40) device which looks like a giantic square about 8 by 8 inches. It suddenly just died, nothing we tried would get it t work and yes there is an internal battery. We know the battery works because all the lights on the top work, but it doesn't allow us to get calls, make calls or even have a dial tone on our phones anymore after many years of use. We decided to switch that dated device which also came with a nano sim card, for a new motorola. I verified that our new phone was compatible through ATT first, it was Motorola G Stylus 5G 2023 unlocked through Motorola itself. Got the phone, called ATT to ask about tranferring the sim in the Wireless Internet (IFWA40) and she stated we would need a new sim after taking my information of what device we had and what device we were going to switch to. She said my number would be transferred to the new phone and the next day I received the new sim card from ATT. Popped it in per the instructions with phone off, turned phone on, the phone doesn't work. I've switch sims to new phones well over 10 years as we have 5 adults kids now, so believe me this is not a new concept for us. I have been on the phone with ATT 3 times in 3 days, going throuh the motions trying to get this phone to work. My online ATT shows the number is activated, but it also shows we still have the Wireless Internet (IFWA40) system, and not the new Motorola. Now I'm told I need to go into the ATT store, but I am so frustrated that I can't just activate my phone online like I've done for almost 10 years now. All the sudden none of the ATT associates that I've already spend 2 hours with can't help me? Seriously?