slow upload speeds

I have AT&T Fiber, and I am having a problem with my upload speeds. Download is fine (800-900mbps). Upload, however, is abysmal (2-5mbps). My hardware is up to date (AMD 3600 based system with 1gbps ethernet). While my uploads were never as good as my downloads, I had been consistently getting 500-600mbps.

One of the reasons I switched to AT&T Fiber was for the upload speeds.

Please help.