Issues with sending messages on iPhone

I recently switched carriers and I'm noticing something strange with sending messages that wasn't happening before.

I can receive messages just fine, but when I send them out, the recipient receives it just fine, but on my end it says that the message is "not delivered" or I get a "Message Send Error" after about a minute. I've tried send message to myself, and the same issue occurs (I receive it immediately, then the "not delivered" error shows up). I've already asked support for my carrier and they said it might have something to do with my phone's settings. I have an iPhone 11 on iOS 18.1.1.

Any help would be appreciated.