Alternatives to AT&T Service for Cellular Backup

Is there any alternatives to using AT&T for Cellular Backup?

Unfortunately, AT&T cellular service is pretty much nonexistent at my house. Has anyone been able to successfully swap out the SIM with another carrier?

I have the same problem. Ring should have contract with all carriers and install sim based on location of installation. Though there are many places where cellular from any carrier is nonexistent. Since moving to current area I switched to Sprint and recently to T-Mobile. Verizon and AT&T aren’t even an option.