Calls being blocked or marked as spam on company caller ID
I work for a company that provides inmate phones. We have 50 or so jails and they all use the same phone number as outbound caller ID. For roughly 2 weeks we've seen a crazy increase in trouble tickets because calls are not going through, and we've found that calls are being blocked before they get to the customer phone or they are being marked as spam. Changing the outbound caller ID makes it work immediately. Confirmed in the office with workers who have ATT phones, none of them have ever had a spam call blocking app, and this only affects ATT and ATT adjacent (cricket, etc) numbers. What is the process to get this reversed?