Bad ATT Cellular backup reception

I was getting ready to switch my alarm to Ring and also incorporate several other Ring products. Then I realize i cannot get a good reception to support cellular backup. Cellular Strengthis next to none. It shows 1 bar usually and sometimes none. With one bar, it's not enough to transition to cellular backup reliablly. It successfully transition maybe once in 10 tries. Base station will just show "offline". Then even if it transitions successfully, I tested it by tripping alarm, it doesn't work reliably. The signal goes to Monitoring fine, but I couldn't disarm it from the app. The siren kept on screening until... Any alternative to ATT cellular service? My current system uses Tmobile and it's fine. I heard Simplisafe has options for customers. I waited for almost an hour for RIng Support and the rep I talked to had to reach out to her "Support team".... So I'm still waiting for someone to get back to me. Any chance this can be solved? An alarm solely rely on wifi is not safe. I can't give up cellular backup. Any alarm should have at least one backup system.