Very slow 5G internet speeds at certain times

I am talking large discrepencies in speed. When at certain times it goes to almost 300 Mbps download and 75 Mbps upload. This is using an ethernet connection, not wifi on my home computer. My gateway shows good to excellent signal strength.Then during peek hours of cell phone use it can drop to 10 Mbps or less download and 1.5 Mbps upload. I have used Wifi Man and Opensignal as well as my own tests to see if what I am receiving is true. This is clearly a a problem with the tower 2 miles away not being able to handle those phone calls and the lower priority of the 5G internet service. I have always gotten the "working on the tower" excuse that has lasted for over a year from T-Mobile tech support. I live alone in a 2 bedroom condo on a terraced hill near the top in a large city suburb. Most of the time I can watch tv without buffering and use my computer for routine internet work even at the slowest speeds. I am trying very hard not to go back to AT&T and fight over their rate increases.