Assistance unblocking our ability to send email to text messages

Hello,

Starting on 3/20/24 we were blocked from sending text messages to our clients who are AT&T customers. Prior to that date, we have been sending our clients email to text messages for years with no issue. We contacted CloudMark, which was providing the bounce back errors, but they told us we need to directly communicate with AT&T. We emailed the errors to abuse_rbl@abuse-att.net. However, we have received no response. It's been several days and we are still seeing the vast majority of our email to texts being blocked. I have tried to call several AT&T support lines, but I'm always told that without an account number no one is able to help us. How can we get this resolved?