Can't receive texts from multiple contacts who are on different carriers.

I switched to AT&T, after being with Sprint/ T-Mobile for 12 years, on July 5th 2022 (2 weeks ago). They shipped my phone and I activated it on the 9th. Ever since activating, I can't receive SMS or MMS from several contacts and can't receivemany short codes. I've called everyday. Sometimes up to 5 times a day. Every time I call they follow their prompts to do the same troubleshooting techniques. A couple times, after a network reset, I'm able to receive one message. Then they stop appearing again. Technical support will then submit a ticket to the engineers who will subsequently close my case with no explaintion or resolve. Now I am pressured to hurry and find a new carrier before my buyer's remorse period is up. I can't remember a time I've felt more remorseful of a purchase.