Well I guess it's possible that the head units degrade over time, but
looks like your testing correctly ATT vs ATT. You could cancel service
and get an external portable hot spot. Not the best solution I know.
Also shot in the dark, have you done a f...
John62 how old is your vehicle? Mine is a 2022 Equinox and has the 4G
LTE service. I assume the older 2G/3G if it still works would be that
slow. If I have 4-5 signal bars then pulling 50-90 meg down is not an
issue.