One potential problem with jumping to another carrier is that it could
prolong the pain.

There probably was some technical problem with the port.
They'll fix it if you keep nagging. In the meantime, check your APN settings and see if you get any better results with disabling 5G or enabling Wi-Fi Calling (VoWiFi). And they might have to do a SIM/eSIM swap to fix it, so be prepared for that possibility.
If it's a physical SIM, and if convenient, you could try moving it to another phone make/model to see if you get any different results. If it's the same problem, it's almost certainly a problem on the carrier side.
I don't think Eight supports call forwarding.

If they do, it's an unpublished feature.