System Upgrade - Dallas Oregon - performance degradation so that it's unusable.

T-Mobile "upgraded" their systems from March 28th-May 16th locally.  Starting almost immediately in March, performance went from 200-300 Mbps download, 50+ Mbps upload, to 4-20 Mbps download and 0.5 Mbps upload.  The tower is 3.42 miles direct line of sight. We have Home Internet, and three 5G phones here. The performance degradation is on all devices. I have made several calls, they "opened a ticket", but, of course, the help line assumes that the problem is on our devices.  We've gotten new SIMs, reset and rebooted everything multiple times.  When much closer to the tower, or in neighboring cities, I get the original 200-300 Mbps performance levels. 

Is there any way to actually effectively contact T-Mobile to determine what the issue is?  I work from here, and am completely dependent on this service, we are otherwise "off-grid", I have no other workable internet access. I've tried other radio providers, including satellite.  The only other possibility that might work is Starlink.  If T-Mobile cannot restore the performance, there is no point in having the Home Internet, and I have to drive into town to work.