iMessage & FaceTime activation is unsuccessful - iPhone 15 Pro

I can't send an iMessage, and every text I send eventually turns into an SMS, but certain people can iMessage me. It's extremely frustrating and confusing, and I have tried all of the basic steps.

1. Signing in/out of iCloud, waiting 24hrs.
2. Turning on and off iMessage.
3. Soft reset.
4. Network Settings reset.

For a few hours it will work but it eventually goes back to saying iMessage activation unsuccessful. I'm going to try a factory reset in the morning and reinstalling a back up to see if it will solve the issue, but I worry it won't. Does anybody have any recommendations? I have seen people talking about reaching out to their carrier, should I reset my eSIM? I would appreciate any ideas!

Thanks!