if you're in the US, give https://www.twilio.com/wireless a try. You're still using the same carriers under the hood but at the very least you're giving money to their business/enterprise side instead of the shitty customer side.
You can't receive texts from other Twilio numbers, which doesn't sound that bad, until you realize that virtually every verification SMS from most services also use Twilio. I wouldn't get 90% of my 2FA SMS codes anymore after trying to use it.
Also, data is super expensive on Twilio Wireless. After one day of just background data (no browsing or streaming) I was charged ~$15 (for the 100MBish of data I used off of Wi-Fi).
There are all kinds of other problems with it too as a cell service.
There are some really good reasons to use Twilio Wireless though, but not for mobile phone service. It's great for IoT hobby projects.
That seems like it would be the easiest thing for them to get working out of all the wireless stuff, did you report that issue to them?
What they didn't tell me, but I assume, is that some popular discord servers require phone verification to limit spam... and if anyone could just use a VoIP number as that phone verification, then that wouldn't work. (It still doesn't work, of course, but they think it does.) I, of course, just want to have an account recovery phone number, but they conflate the two uses of the phone number (person identifier, versus arbitrary second factor).
TL;DR, a lot of places are dumb and intentionally prevent you from using any sort of "recyclable" phone number. It helps them keep up the illusion that a phone number uniquely identifies exactly one person. Maybe that's true in South Korea, but it isn't here. So it just screws legitimate users for no reason.
You absolutely can receive texts from other Twilio numbers. It's shortcodes you can't receive from (which is definitely a problem).
Your data would be cheaper if you set the billing mode to "individual" (and not "pooled"), which will charge you for blocks of 1GB at a time. Having said that, data will still probably not be cheaper than a normal retail cell plan.
Aside from that, another issue is lack of MMS support. Twilio Wireless is designed for IoT use cases, so general cell phone use isn't something it's optimized for.
(Source/Disclosure: I'm the engineer who built the first version of Twilio Wireless.)