Ooooh man, I'd be pissed too. I would have left them too and ever since I'd be looking for the class action suit that I'm sure is in the works. If it isn't, maybe it should be.
Verizon carried that phone with 5G branding, if they ended up not using the tech in favor of something else --- well, then that's okay too (technology changes) but they need to reimburse the customers who thought they were future proofing themselves. You can't sell it branded as 5G then later say, "oh, it's 5G but not the kind we use." -- "WTF! I bought it from YOU!" "I think they might use those bands in Malaysia or Cambodia, maybe think of moving."
I had something similar but different recently happen with Verizon. I have a pixel 2, which I still love. Came out October 2017. So a little over 4 years old now. Google stopped updates for it last year. But still, overall it's a great device. Fast, responsive, does what you tell it to do... and Verizon will have 4G for a long time, so this device should remain compatible, right?
WRONG! As they retire the 3G CDMA network they're also killing all 4G non-VoLTE (Voice over LTE) devices December 31st 2022. They gave a warning but nothing else. Even $300 off would have made me happy, come on - SOMETHING! Basically, I got "you'll be kicked off the network unless you upgrade."
In my case, I needed to upgrade. Was planning one soon anyway (really shouldn't have gone this long in the business I'm in but it's such an awesome device!). But for most people, my Pixel 2 is still a perfectly good device - great even. They could allow it to continue to use data... but no.
I ended up with the S22 Ultra but am still walking around my house with my Pixel 2... haha.
All of the best devices are always FORCED to die eventually. More planned, forced obsolescence is all we can expect in the future.